(Meth) acrylic acid type polymer and unsaturated polyalkylene glycol type copolymer, and methods for production thereof

ABSTRACT

This invention concerns a (meth)acrylic acid type polymer, wherein the value S representing the quantity of an sulfur element introduced which is defined by the formula, S=(quantity of S contained in polymer)/(total quantity of S)×100, is not less than 35. This (meth) acrylic acid type polymer is a water-soluble polymer of a low molecular weight which has only a small impurity content, entails no precipitation of an impurity during the preservation at a low temperature, and excels in dispersibility, chelating ability, and an anti-gelling property.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.10/262,985, filed Oct. 2, 2002, now U.S. Pat. No. 6,998,453 the entiretyof which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to (meth)acrylic acid type polymers usedadvantageously for such applications as water type dispersants,descaling agents, and detergent builders, a method for the productionthereof, and a detergent using thereof.

This invention also relates to unsaturated polyalkylene glycol typecopolymers used advantageously for such applications as water typedispersants, descaling agents, cement additives, and detergent builders,a method for the production thereof, and detergents using thereof.

2. Description of the Related Art

<Prior Art Concerning (Meth)acrylic Acid Type Polymer>

Of such water-soluble polymers as polyacrylic acid and polymaleic acid,those which have low molecular weights have been heretofore usedadvantageously for dispersants directed toward inorganic pigments andmetal ions, descaling agents, and detergent builders. As a means forobtaining such water-soluble polymers of low molecular weights, themethods which are disclosed, for example, in JP-A-64-38403 andJP-A-05-86125 have been known.

The method disclosed in JP-A-64-38403, in radically polymerizing one ormore water-soluble vinyl monomer (ethylenic monomer) with the use of awater-soluble azo type radical polymerization initiator, contemplatesthe presence in the reaction system of 0.1–30 mol % of sulfurous ionbased on the quantity of the monomer. The monomer used in this case doesnot need to be particularly restricted but is only required to be awater-soluble vinyl monomer. The use of this method allows production ofwater-soluble polymers of low molecular weights not less than severaltens of thousand with satisfactory reproducibility.

JP-A-05-86125 obtains a water-soluble polymer formed of not less than 95mol % of acrylic acid or an acrylate by subjecting acrylic acid or anacrylate to aqueous solution polymerization while retaining the pH ofthe solution in the range of 6–9 (under the neutral condition). At thistime, the number average molecular weight of the polymer is in the rangeof 300–10000 and the degree of dispersion is in the range of 1.3–2.3.Since the water-soluble polymer obtained by this method has a lowmolecular weight and has a degree of dispersion in a narrow range(having a narrow molecular weight distribution), it exhibits a highdegree of dispersibility and is used advantageously for variousdispersants and detergent builders.

JP-B-60-24806 discloses a method for producing an acrylate type lowmolecular weight polymer. The method of JP-B-60-24806 consists insubjecting (A) an alkali metal salt of acrylic acid, (B) acrylamide or2-hydroxyethyl (meth)acrylate, and (C) a hydrophilic monomer capable ofcopolymerizing with the (A) and (B) components mentioned above in aprescribed ratio to aqueous solution polymerization. The polymerizationconditions are not less than 10 liters of air per mol of the (A)component and a polymerization temperature of not higher than 80° C.

The acrylate type water-soluble polymer obtained by this method has amolecular weight in the range of 500–100000 and a narrow molecularweight distribution. Further, the water-soluble polymer entrains noimpurity and incurs coloration only slightly. Moreover, the terminal ofthe straight chain or the side chain of this water-soluble polymer iscapable of introducing 0.5–1.5 sulfonic groups per molecule. Thewater-soluble polymer, therefore, excels in dispersibility and thechelating property and can be advantageously used for dispersantsdirected to inorganic pigments, detergent builders, cleaning agents, anddescaling agents.

As a technique for producing a low molecular polymer which is not such awater-soluble polymer as mentioned above, the method disclosed in U.S.Pat. No. 3,646,099 may be cited. The low molecular weight polymer whichis disclosed in this publication is intended for use inelectroconductive coating materials. It is formed by polymerizing(meth)acrylonitrile and a hydrophobic monomer and has to fulfill theessential requirement that the hydrophobic monomer be in a proportion ofnot less then 40mol %. By this method, it is made possible to produce apolymer having a molecular weight of not more than 25000.

By the techniques disclosed in JP-A-64-38403 and JP-A-05-86125, however,it is difficult to introduce a sulfonic group quantitatively into theterminal or the main chain of the relevant polymer. The water-solublepolymers obtained by these techniques, therefore, hardly deserve to berated fully excellent in the dispersibility and the anti-gellingproperty and are not optimum for dispersants, detergent builders,cleaning agents, and descaling agents.

By the technique which is disclosed in JP-B-60-24806, it is madepossible to obtain a water-soluble polymer having a sulfonic groupintroduced to a certain degree therein. Since the monomer used in thistechnique is an acrylate (alkali metal salt), the system ofpolymerization reaction is substantially completely neutralized.

In the polymerization performed in such a neutral state as uses anacrylate, when the concentration of a solid component in the reactionsystem is heightened, the viscosity of the reaction solution tends toincrease conspicuously in accordance as the polymerization proceeds andthe molecular weight of the produced polymer tends to increase to acopious degree. Thus, the technique taught in JP-B-60-24806, when usedin the polymerization of a monomer, is at a disadvantage in failing toproduce a polymer of a low molecular weight under the condition of ahigh concentration and incurring a decline in the efficiency ofproduction.

Further, by the technique disclosed in U.S. Pat. No. 3,646,099, it ismade possible to produce a polymer of a low molecular weightadvantageously. The technique disclosed in U.S. Pat. No. 3,646,099,however, is directed toward producing a polymer using a hydrophobicmonomer in a proportion of not less than 40 mol %. The low molecularweight polymer consequently obtained is not soluble in water.Specifically, the technique disclosed in U.S. Pat. No. 3,646,099 isdirected toward producing a low molecular weight polymer for use inelectroconductive coating materials. By simply substituting the monomerfor a water-soluble monomer, it is not possible to producesatisfactorily a water-soluble polymer.

In order for the water-soluble polymer of a low molecular weightmentioned above to be used advantageously for dispersants, descalingagents, and detergent builders, the water-soluble polymer is preferredto excel in the anti-gelling property, i.e. quality of rejectinggelation, besides the dispersibility and the Ca-binding capacity whichare inherent in the water-soluble polymer. The techniques disclosed inthe publications mentioned above, however, are incapable of producing awater-soluble polymer excelling in the anti-gelling property. They are,therefore, incapable of obtaining a water-soluble polymer possessingproperties which fully befit dispersants, descaling agents, anddetergent builders.

Thus, the methods described above are not fully satisfactory for thewater-soluble polymer of a low molecular weight which excels in thedispersibility and the anti-chelating property and excels in theanti-gelling property as well and for the purpose of effecting efficientproduction of the water-soluble polymer.

The present inventors have discovered that a (meth)acrylic acid typepolymer of a low molecular weight excelling in the dispersibility andthe chelating property and in the anti-gelling property as well can beefficiently produced by polymerizing a monomer having a sulfonic groupquantitatively introduced into the terminal and containing (meth)acrylicacid under an acidic condition. The (meth) acrylic acid type polymermentioned above is a polymer which is formed by polymerizing 50–100 mol% of (meth)acrylic acid and 0–50 mol % of a water-solublemonoethylenically unsaturated monomer capable of copolymerizing with the(meth)acrylic acid in an aqueous solution and which has a sulfonic grouplinked to the terminal thereof. This (meth) acrylic acid type polymer ischaracterized by the fact that the value Q representing the anti-gellingability defined by the formula, Q=Degree of gelation×10⁵/weight averagemolecular weight, is less than 2.0. The (meth)acrylic acid type polymeris a water-soluble polymer of a low molecular weight which excels in theanti-gelling property and in the dispersibility and the chelatingability as well. In the method for the production of this polymer, thehydrophilic monomer containing not less than 50 mol % of (meth)acrylicacid is used in a proportion of not less than 60 mol %, the pH of thesystem used for polymerizing the monomer is less than 5, and the degreeof neutralization is less than 40 mol %. The monomer mentioned above ispolymerized by using as an initiator the combination of one or morespecies respectively of persulfate and bisulfite. More preferably, ahydrophilic monomer containing at least 50 mol % of (meth)acrylic acidis used in a proportion of not less than 60 mol % and, while thismonomer is added dropwise to be polymerized under such acidic conditionsas a pH of less than 5 and a degree of neutralization of less than 40mol %, the solid concentration of the system of polymerization at thetime that the dropwise addition of the monomer is completed is set at alevel of not less than 40 mass % and the weight average molecular weightis set at a level in the range of 3000–15000. The present inventors havefound that in consequence of the polymerization, a water-soluble polymerof a low molecular weight excelling in the anti-gelling property and inthe dispersibility and the chelating ability can be produced with highefficiency. This knowledge has been proposed in JP-A-11-315115.

The water-soluble polymer of JP-A-11-315115 has been finding extensiveutility because it is possessed of properties befitting dispersants,descaling agent, and detergent builders.

<Prior Art Concerning Unsaturated Polyalkylene Glycol Type Copolymer>

It has been known that copolymers formed by using an unsaturatedpolyalkylene glycol type monomer are useful as builders for liquiddetergents. For example, the copolymers of such unsaturated polyalkyleneglycol type monomers as ethylene oxide adducts of 3-methy-3-buten-1-oland such unsaturated monocarboxylic acid type monomers as (meth) acrylicacid are useful as liquid detergent builders. As a means to obtain sucha copolymer, the method disclosed in JP-A-2002-60785, for example, hasbeen known.

The method disclosed in the publication mentioned above, incopolymerizing a monomer component essentially containing either anunsaturated monocarboxylic acid type monomer or an unsaturateddicarboxylic acid type monomer and an unsaturated polyalkylene glycoltype monomer, effects the necessary polymerization by using a persulfateor hydrogen peroxide as an initiator. When this method is used, acopolymer having a molecular weight up to several tens of thousand canbe obtained with high reproducibility.

The polymer which is obtained by this method excels in the compatibilitywith a liquid detergent and in the dispersibility and can beadvantageously used for detergent builders, particularly liquiddetergent builders.

As a technique for producing a (meth) acrylic acid type polymer of a lowmolecular weight, which is not a polymer containing an unsaturatedpolyalkylene glycol type monomer, the method disclosed in JP-A-11-315115may be cited.

By the method disclosed in the publication mentioned above, when amonomer component essentially containing a (meth)acrylic acid typemonomer is polymerized, the polymerization is effected at a highconcentration of not less than 40 mass % by using a persulfate or abisulfite as an initiator. By using this method, it is made possible toobtain a low molecular weight polymer having a molecular weight of notmore than several tens of thousand with high reproducibility.

The polymer which is obtained by this method has a narrow molecularweight distribution and incurs coloration only slightly. Further, thispolymer has sulfur oxygen acid quantitatively introduced into theterminal of the straight chain or to the side chain thereof. Thus, thispolymer excels in the dispersibility and the anti-gelling property andcan be advantageously used for dispersants directed toward inorganicpigments, detergent builders, cleaning agents, and descaling agents.

When a copolymer of a (meth)acrylic acid monomer and an unsaturatedpolyalkylene glycol type monomer is produced by using the techniquedisclosed in JP-A-2002-60785, however, the polymer has the molecularweight thereof increase unless the polymerization concentration islowered to the order of 20 mass %. The polymerization solution possiblysuccumbs to gelation. Thus, the polymerization concentration must belowered at a sacrifice of productivity. Further, the aqueous solution ofpolymer consequently obtained has an inferior hue. In the light of thesefactors, the polymer does not deserve to be rated as optimum fordetergent builders.

Further, by using the technique disclosed in JP-A-11-315115, it is madepossible to produce a polymer of a low molecular weight in a highconcentration. Since this technique is directed toward producing apolymer by mainly using a (meth) acrylic acid type monomer, the polymerobtained by the technique has low compatibility with liquid detergents.By the technique disclosed in JP-A-11-315115, therefore, it is difficultto produce a polymer suitable for liquid detergent builders.

By such conventional techniques as these, it has never been madepossible to produce a polymer of a low molecular weight excelling inhue, compatibility with liquid detergents, dispersibility, andanti-gelling property at a high concentration with satisfactoryefficiency.

<Problems Concerning (Meth)acrylic Acid Type Polymer>

The present inventors, not satisfied with the development of this noveltechnique, have further continued a study concerning the (meth)acrylicacid type polymer and the method for production thereof disclosed inJP-A-11-315115. It has been consequently ascertained {circle around (1)}that the bisulfite used as an initiator emits sulfur dioxide in a largequantity during the course of the production, the generated sulfurdioxide dissolves in the liquid phase and forms an impurity, the sulfurdioxide which has escaped solution in the liquid phase is dischargedfrom the system in a large quantity, and the discharged sulfur dioxidegives rise to a new problem of necessitating a costly treatment whichcomprises recovering this harmful gas with a proper adsorbent anddiscarding the spent adsorbent and {circle around (2)} that since thebisulfite as an initiator escapes in the form of sulfur dioxide andincurs loss of effect, the molecular weight of the polymer is notlowered, the total quantity of the initiator required is increased, theproduction is suffered to form a large quantity of an impurity, the highperformance owned inherently by the produced (meth)acrylic acid typepolymer is not manifested fully satisfactorily, and a new problem ofdegrading quality and inducing precipitation of an impurity during thepreservation at a low temperature is encountered.

An object of this invention, therefore, is to provide a (meth)acrylicacid type polymer which is a water-soluble polymer of a low molecularweight excelling in dispersibility, chelating ability, and anti-gellingproperty. The (meth)acrylic acid type polymer of this invention has aprominently allayed impurity content and a further enhanced performance.Further, the (meth)acrylic acid type polymer of this invention possessesan outstanding ability to preserve constantly stably the highperformance endowed during the course of production without beingaffected by the environment of preservation and suffers neither fromdegradation of quality nor precipitation of an impurity during thepreservation at a low temperature.

Another object of this invention is to provide a method for producing a(meth)acrylic acid type polymer which is a water-soluble polymer of alow molecular weight excelling in dispersibility, chelating ability, andanti-gelling property. By the method of this invention for theproduction of a (meth)acrylic acid type polymer, it is made possible toproduce a (meth)acrylic acid type polymer which allays generation of alarge quantity of sulfur dioxide and generation of an impurity andacquires a further enhanced performance.

Still another object of this invention is to provide a detergent formedby using (as a high performance detergent builder) a (meth)acrylic acidtype polymer which is a water-soluble polymer of a low molecular weightexcelling in dispersibility, chelating ability, and anti-gellingproperty. The detergent of this invention acquires a further enhancementof performance and quality. Further, the detergent of this invention ispossessed of a high ability of effecting stable preservation incapableof being effected by the environment of preservation.

<Problems Concerning Unsaturated Polyalkylene Glycol Type Copolymer>

The unsaturated polyalkylene glycol type copolymer disclosed inJP-A-2002-60785 indeed excels in compatibility with liquid detergentsand dispersibility and nevertheless betrays deficiency in hue and inproductivity as well. Meanwhile, the polymer disclosed in JP-A-11-315115is deficient in compatibility with liquid detergents. The problem to befulfilled by this invention, therefore, resides in providing a liquiddetergent grade builder, a cement additive, and a detergent containingthe liquid detergent grade builder which excels in compatibility withliquid detergents, dispersibility, and hue.

Further, the object to be fulfilled by this invention consists inproviding a method for polymerizing an unsaturated polyalkylene glycoltype copolymer excelling in compatibility with liquid detergents,dispersibility, and hue in a high concentration with high productivity.

SUMMARY OF THE INVENTION

The present inventors have made a diligent study concerning a (meth)acrylic acid type polymer of a low molecular weight excelling indispersibility, chelating ability, and anti-gelling property and amethod for the production thereof with a view to fulfilling the objectsmentioned above. Consequently, they have found that while the(meth)acrylic acid type polymer is indeed a water-soluble polymer of alow molecular weight combining dispersibility, chelating ability, andanti-gelling property, it has been unable to manifest the inherentlyowned outstanding properties fully satisfactorily. They have also foundthat by the prolonged polymerization at a low temperature which appearsto be deficient in productivity, it is made possible to decrease thedischarged sulfur dioxide and decrease the impurity as well bydecreasing the amount of the initiator to be used (preferably by furtherlowering the degree of neutralization during the process ofpolymerization). As a result, it is made possible to improve remarkablythe properties owned by the (meth)acrylic acid type polymer, furtherallay the degradation of quality and the precipitation of an impuritiesduring the preservation at a low temperature, and permit constantlystable retention of the high quality imparted in the course ofproduction without being affected by the environment of preservation(namely allow thorough manifestation of the inherently owned qualitywithout being degraded). This invention has been perfected based on theknowledge.

The present inventors have further discovered a method for polymerizinga monomer containing an unsaturated polyalkylene glycol type monomer byintroducing sulfur oxygen acid to the terminal thereof in a highconcentration of not less than 40 mass %. By this method, it is madepossible to produce efficiently an unsaturated polyalkylene glycol typecopolymer of a low molecular weight excelling in compatibility withliquid detergents, dispersibility, chelating ability, and anti-gellingproperty and an aqueous solution of this copolymer. They have eventuallyperfected this invention based on this knowledge.

The first aspect of this invention is directed toward a (meth)acrylicacid type polymer, wherein the value S representing the quantity of ansulfur element introduced which is defined by the formula, S=(quantityof S contained in polymer)/(total quantity of S)×100, is not less than35.

The second aspect of this invention is directed toward a method for theproduction of a (meth)acrylic acid type polymer, characterized by usingas an initiator the combination of one or more species respectively of apersulfate and a bisulfite, wherein the bisulfite is used in aproportion in the range of 0.5–5 by mass ratio relative to the mass ofthe persulfate taken as 1, the total quantity of the persulfate and thebisulfite to be added to the reaction system of polymerization is in therange of 2–20 g per mol of the monomer to be polymerized, and thepolymerization temperature is in the range of 25–99° C.

The third aspect of this invention is directed toward an unsaturatedpolyalkylene glycol type copolymer, wherein the copolymer is produced bycopolymerizing a (meth)acrylic acid type monomer A and an unsaturatedpolyalkylene glycol type monomer B, the copolymer possesses sulfuroxygen acid at the terminal thereof, and the value S representing thequantity of the sulfur element introduced which is defined by theformula, S=(quantity of S contained in the polymer)/(total quantity ofS)×100, is not less than 3.

The fourth aspect of this invention is directed toward a method for theproduction of an unsaturated polyalkylene glycol type copolymer by thecopolymerization of a (meth)acrylic acid type monomer A and anunsaturated polyalkylene glycol type monomer B, wherein the combinationof one or more species respectively of a persulfate and a bisulfite isused as an initiator.

DETAILED DESCRIPTION OF THE INVENTION

The above and other objects, features, and advantages of the presentinvention will become clear from the following description of thepreferred embodiments.

Now, the embodiment of this invention will be described in detail below.

The first aspect of this invention is directed toward a (meth)acrylicacid type polymer, wherein the value S representing the quantity of ansulfur element introduced which is defined by the formula, S=(quantityof S contained in polymer)/(total quantity of S)×100, is not less than35. Preferably, the polymer is formed by polymerizing a monomercontaining 50–100 mol % of (meth)acrylic acid and 0–50 mol % of awater-soluble monoethylenically unsaturated monomer capable ofcopolymerizing with the (meth) acrylic acid in an aqueous solution.Further, in the (meth)acrylic acid type polymer which has such asulfur-containing group as a sulfonic group linked to the terminalthereof and which has a value Q of not less than 3.0 for theanti-gelling ability, defined by the formula, Q=degree ofgelation×10⁵/weight average molecular weight, the value S representingthe quantity of the sulfur element incorporated is preferred to be notless than 35. It has been found by the present inventors that thepurpose of enabling the (meth)acrylic acid type polymer of a lowmolecular weight excelling in dispersibility, chelating ability, andanti-gelling property to acquire a value S of not less than 35 for thequantity of the sulfur element, to be introduced is accomplished bycontrolling the polymerization temperature and the degree ofneutralization within prescribed ranges during the course of production.By this control, it is made possible to repress the generation of sulfurdioxide in a large quantity and further repress the generation of animpurity. The polymer obtained through the process of productionmentioned above and consequently allowed to acquire a value S of notless than 35 for the quantity of the sulfur element to be introduced hasan extremely small impurity content. It is also made possible to repressthe degradation of quality due to the impurity to a remarkably lowdegree. The precipitation of an impurity during the retention of thepolymer in the form of an aqueous solution at a low temperature can berepressed also to a remarkably low degree. The polymer under discussionexcels the (meth)acrylic acid type polymer proposed by the presentinventors and disclosed in JP-A-11-315115 in the Ca-binding capacity.The polymer is colorless and transparent and excellent in hue ascompared with the conventional aqueous solution of the (meth) acrylicacid type polymer. Thus, this invention promises further improvement ofthe quality.

In the (meth)acrylic acid type polymer, the value S representing thequantity of the sulfur element introduced generally exceeds 35 andpreferably falls in the range of 35–70 and more preferably in the rangeof 40–60. If the value S representing the quantity of the sulfur elementintroduced falls short of 35, the shortage will be at a disadvantage innot allowing the quantity of an initiator required for thepolymerization to be decreased satisfactorily, consequently preventingthe formation of an impurity and the generation of sulfur dioxide frombeing effectively allayed, and possibly incurring the degradation ofquality and the precipitation of an impurity during the preservation ata low temperature. The upper limit of the value S representing thequantity of the sulfur element introduced does not need to beparticularly restricted.

Incidentally, the expression “quantity of S contained in the polymer” asused in the preceding definition of the value S representing thequantity of the sulfur element introduced refers to the quantity of S,which is contained in the (meth) acrylic acid type polymer. Morespecifically, the expression refers to the quantity of S contained in amacromolecular component formed of a (meth) acrylic acid type polymerwhich remains after such low molecular components as an impurity and aninitiator fragment have been removed from the aqueous solution of a(meth) acrylic acid type polymer obtained by polymerization andsubjected to adjustment of a solid content concentration and which isdetermined by the method of dialysis specifically described in theworking example cited herein below. In other words, the expression maywell be interpreted as referring to the quantity of S which isintroduced into the terminal or the side chain of the (meth)acrylic acidtype polymer in the form of such a sulfur-containing group as a sulfonicgroup. It maybe safely inferred, therefore, that the proportion of thequantity of the S component contained originally in the used initiatorwhich is introduced advantageously into the polymer in consequence ofthe reaction of polymerization increases in accordance as the value Srepresenting the quantity of the sulfur element introduced is increased.The term “total quantity of S” used in the definition of the value Srepresenting the quantity of the sulfur element introduced refers to thequantity of whole S contained in the phase in which the (meth)acrylicacid type polymer is present. The reason for not-using the quantity of Sin the raw material used for the polymerization from the total quantityof S is that the quantity of S (sulfur component) which has beendischarged out of the system as sulfur dioxide is absent from the(meth)acrylic acid type polymer (aqueous solution) and has nopossibility of being precipitated as an S-containing impurity during thepreservation at a low temperature.

The term “(meth)acrylic acid type polymer” as used in the presentinvention refers to a comprehensive concept covering an aqueous solutioncontaining a (meth) acrylic acid type polymer obtained bypolymerization, the aforementioned aqueous solution having such anaqueous solvent as water added thereto or removed therefrom in a properquantity for the purpose of adjusting a solid content concentration, asolid substance obtained by depriving the aqueous solution of theaqueous solvent and drying the residue, the aqueous solution of a(meth)acrylic acid type polymer obtained by properly depriving anaqueous solution containing a (meth)acrylic acid type polymer resultingfrom polymerization of an impurity and purifying the residue, theaqueous solution having an aqueous solvent added thereto or removedtherefrom for the purpose of adjusting a solid component concentration,a (meth)acrylic acid type polymer dried till a solid state, and theaqueous solution optionally having proper additives such as, forexample, preservation stabilizers (absorbent for ultraviolet light andantioxidant), coloring agents, antistatic agents, slip additives,fillers, flame retardants, and foaming agents incorporated therein inproportions incapable of adversely affecting the quality of the(meth)acrylic acid type polymer obtained by polymerization. In short,the (meth)acrylic acid type polymer does not need to be particularlydiscriminated on account of shape and composition but is only requiredto contain a (meth)acrylic acid type polymer. The (meth)acrylic acidtype polymer of this invention, therefore, embraces the case of formingthe polymer solely of a purified (meth)acrylic acid type polymer. Thus,the (meth)acrylic acid type polymer of this invention has only tosatisfy the aforementioned value S representing the quantity of thesulfur element introduced and ought to be interpreted in the broadestpossible sense without reference to the designation. It ought not to beinterpreted (restricted) narrowly as the solid component of a(meth)acrylic acid type polymer or the aqueous solution thereof. Fromthe viewpoint of simplifying the process of production, it iscommendable to utilize the aqueous solution containing a (meth)acrylicacid type polymer obtained by polymerization directly as a dispersant, adescaling agent, and a detergent builder, for example. From theviewpoint of lowering the cost of transportation, it is commendable totransport the polymer in the form of a solid substance instead of such abulky form of an aqueous solution and optionally transform the solidsubstance into an aqueous solution when the polymer is compounded as adispersant, a descaling agent, or a detergent builder, for example. Fromthe viewpoint of stabilizing the product in quality and stabilizing thepreservation of the product, it is commendable to reduce the aqueoussolution containing a (meth)acrylic acid type polymer obtained bypolymerization to a finished product by depriving the aqueous solutionof an impurity. Thus, the polymer may be suitably endowed with such ashape and a composition as befit the purpose of use. That is, the(meth)acrylic acid type polymer does not need to be particularlyrestricted on account of shape and composition but has only to be suchthat the polymer obtained by polymerization fulfills the requirementthat the value S representing the quantity of the sulfur elementintroduced determined by the analysis of a prescribed method(specifically described in a working example hereinafter) be not lessthan 35.

The (meth)acrylic acid type polymer according to this invention ispreferred to fulfill the requirement that R of the formula, R=(theintegral ratio of signals of 2.3–4.3 ppm)/(the integral ratio of 0.8–4.3ppm including a signal of PSA)×100, in the ¹H-NMR spectrum be in therange of 1–10 besides satisfying the aforementioned value S representingthe quantity of the sulfur element introduced. As a result, it is madepossible to acquire an effect equivalent to or higher than the effect ofoperation obtained by satisfying the requirement concerning theaforementioned value S representing the quantity of the sulfur elementintroduced. That is, the (meth)acrylic acid type polymer fulfillingthese requirements has an extremely small content of impurity and hasthe degradation of quality due to the impurity repressed to a remarkablylow degree. Further, such a (meth)acrylic acid type polymer as this hasthe precipitation of an impurity during the preservation thereof in theform of an aqueous solution at a low temperature repressed to aremarkably low degree. Further, this (meth)acrylic acid type polymerexcels in anti-gelling property and also excels in the Ca-bindingcapacity and enjoys an excellent hue. Thus, the further improvement ofthe quality can be materialized.

The value R of the (meth)acrylic acid polymer is generally in the rangeof 1–15, preferably in the range of 2–12, and more preferably in therange of 3–10. If this value R falls short of 1, the shortage will be ata disadvantage in degrading the anti-gelling ability, unduly increasingthe total quantity of peaks originating in the organic matter of the(meth)acrylic acid type polymer (mostly of the quantities of peaksoriginating in such an impurity as an initiator fragment) relative tothe quantity of peaks originating in the quantity of S contained in the(meth)acrylic acid type polymer, hardly allowing efficient incorporationof such a sulfur-containing group as a sulfonic group into the(meth)acrylic acid type copolymer, consequently inducing degradation ofquality, and possibly preventing the effect of allaying theprecipitation of an impurity during the preservation of the polymer inthe form of an aqueous solution at a low temperature from beingmanifested fully satisfactorily. Conversely, if the value R mentionedabove exceeds 15, the excess will be at a disadvantage in undulydecreasing the molecular weight and also decreasing the quantity ofcarboxylic acid and degrading the chelating ability.

Here, the integral ratio of the signals of 2.3–4.3 ppm includes suchpeaks as originate in the quantity of S contained mainly in the(meth)acrylic acid type polymer. Meanwhile, the integral ratio of0.8–4.3 ppm including the signal of PSA include all the peaksoriginating in the organic matter of the (meth) acrylic acid typepolymer. The acronym “PSA” as used herein stands for sodiumpolyacrylate. The object sample of the ¹H-NMR spectrum means the aqueoussolution containing the (meth)acrylic acid type polymer used for theanalysis. To be specific, the object sample of the ¹H-NMR spectrum isprepared, as described specifically in a working example cited hereinbelow, by subjecting 1 g of a given (meth)acrylic acid type polymerobtained by polymerization to vacuum drying till the solvent componentremaining therein is thoroughly removed.

Then, the (meth)acrylic acid type polymer according to this inventionhas to fulfill the requirement that the heavy metal ion concentration isin the range of 0.5–10 ppm besides satisfying the aforementioned value Srepresenting the quantity of the sulfur element introduced andpreferably further the value R. As a result, it is made possible todecompose the peroxide used during the course of polymerization anddecrease (decompose) the initiator (peroxide) persisting in the(meth)acrylic acid type polymer and enhance the hue (colorless andtransparent).

Here, the heavy metal ion concentration of the (meth)acrylic acid typepolymer is generally in the range of 0.05–10 ppm, preferably in therange of 0.1–8 ppm, and more preferably in the range of 0.15–5 ppm. Ifthe heavy metal ion concentration falls short of 0.05 ppm, the shortagewill be at a disadvantage in precluding the acquisition of the effectmentioned above, preventing the quantity of the initiator (peroxide)from being decreased fully satisfactorily, making it necessary when the(meth)acrylic acid type polymer is employed for such a use as demands anexcellent hue to decompose or remove such an impurity as an initiatorpossibly persisting in the (meth)acrylic acid type polymer, andconsequently incurring an extra cost for purification. This shortage,when the initiator (peroxide) is suffered to survive in a large quantityin the (meth)acrylic acid type polymer, possibly incurs the problem ofsafety (stimulation of the skin), depending on the kind of use andlikewise necessitates removal of an impurity for the sake ofpurification. Conversely, if the heavy metal ion concentration exceeds10 ppm, though the excess indeed allows such an impurity as theinitiator persisting in the (meth)acrylic acid type polymer to bedecomposed or removed fully satisfactorily, it nevertheless willpossibly induce gelation of the polymer and, because of the emanation ofthe color of heavy metal, impose a restriction on the application of thepolymer to such a use as demands an excellent hue.

The heavy metal ion mentioned above does not need to be particularlyrestricted. As concrete examples of the heavy metal ion, iron ion,nickel ion, chromium ion, and molybdenum ion may be cited. Owing to theexcellence in safety, iron ion and nickel ion prove advantageous andiron ion proves particularly favorable. For the purpose of addition tothe polymer, such a heavy metal ion may be introduced into the systemprior to the start of the polymerization or after the start of thepolymerization. The heavy metal ion which is liquated from a device usedin the process of production may be incorporated at a prescribed ionconcentration into the polymer.

Incidentally, such a heavy metal ion as this does not need to bechemically or physically bound as part of the (meth)acrylic acid typepolymer but is only required to be present in the (meth)acrylic acidtype polymer.

Then, the (meth)acrylic acid type polymer according to this invention ispreferred to fulfill the requirement that the value Q of the formula,Q=degree of gelation×10⁵/weight average molecular weight, be less than3.0 besides satisfying the aforementioned value S representing thequantity of the sulfur element introduced and further preferably thevalue R or the iron ion concentration. Heretofore, the polymerpossessing an anti-gelling property used to have a particularly lowmolecular weight among other polymers having a low molecular weight. Inorder for this polymer to acquire a satisfactory anti-gelling property,it has been necessary to decrease further the molecular weight of thispolymer which originally has a low molecular weight. For the polymerwhich has an unduly small molecular weight, however, it is difficult toincorporate such a sulfur-containing group as a sulfur ionquantitatively into the terminal or the side chain of the polymer,specifically in such a quantity as satisfies the value S representingthe quantity of the sulfur element introduced as defined above. Thus,the polymer is incapable of manifesting fully satisfactorily thedispersing ability and the descaling ability and cannot beadvantageously used for a dispersant, a descaling agent, or a detergentbuilder. In contrast thereto, the (meth)acrylic acid type polymeraccording to this invention has a sulfur-containing group quantitativelyintroduced in the terminal or the main chain of the polymer. To bespecific, it has such a sulfur-containing group as a sulfonic groupintroduced therein in such a quantity as satisfies the value Srepresenting the quantity of the sulfur element introduced as definedabove. As a result, the (meth)acrylic acid type polymer is enabled tomanifest an excellent anti-gelling property notwithstanding it hasacquired a large molecular weight as compared with the conventionalpolymer having an anti-gelling property. That is, when the value Smentioned above is satisfied and the value Q representing theanti-gelling ability as well is confined within the range specifiedabove, the (meth)acrylic acid type polymer is enabled, when applied sosuch uses as an aqueous dispersant, a descaling agent, or a detergentbuilder, to reject gelation and manifest an exceptionally satisfactoryanti-gelling property and consequently the Ca-binding capacity. Thus, itcan be advantageously applied to such uses as an aqueous dispersant, adescaling agent, or a detergent builder. Specifically since this polymeris capable of rejecting the gelation under the circumstance of use andfurther under the circumstance of the preservation subsequently to themixing (compounding) with other components, the finished product of thispolymer is enabled to enhance further the quality and the stabilizationof quality.

Here, the value Q representing the anti-gelling ability is generallyless than 3.0, preferably less than 2.7, and more preferably less than2.5. If this value Q exceeds 3.0, the excess will possibly result inrestricting the uses to be found for the finished product owing to theinsufficiency of the anti-gelling ability. Incidentally, the lower limitof this value Q does not need to be particularly restricted.

In the production of the conventional water-soluble polymer of a lowmolecular weight exhibiting an anti-gelling property, the initiator tobe added to the reaction system of polymerization is required to be in alarger amount than when the polymer of a higher molecular weight isproduced. The (meth) acrylic acid type polymer proposed formerly by thepresent inventors as published in JP-A-11-315115 can repress thisincrease in the quantity of the initiator to be added to the reactionsystem of polymerization because it has a comparatively large molecularweight. Such a (meth) acrylic acid type polymer as this, therefore, ishighly advantageous in terms of cost as compared with the conventionalwater-soluble polymer exhibiting the anti-gelling property. The presentinvention is capable of forming a (meth)acrylic acid type polymer havingan equal value Q of the anti-gelling property in spite of a furtherdecrease in the quantity of the initiator as compared with the(meth)acrylic acid type polymer proposed formerly in JP-A-11-315115.Thus, this polymer is enabled to decrease further the quantity of theimpurity due to the initiator and attain further improvement of quality.Moreover, the further cut of the cost can be accomplished.

Here, the anti-gelling property is calculated as the value Qrepresenting the anti-gelling ability and is rated based on the resultof the calculation. The value Q representing the anti-gelling ability iscalculated based on the following formula using the degree of gelationand the weight average molecular weight of the (meth)acrylic acid typepolymer.Q=Degree of gelation×10⁵/weight average molecular weight

For the purpose of determining the “degree of gelation” in the formulagiven above, the known method for measuring the degree of gelation of a(meth)acrylic acid type polymer can be advantageously used.Specifically, a test solution is prepared by adding a low-concentrationaqueous solution (having a solid component concentration of 1 mass %,for example) of the (meth)acrylic acid type polymer according to thisinvention and an aqueous calcium chloride solution to a buffer solutionand mixing them together. The degree of gelation of the (meth)acrylicacid type polymer can be determined by allowing the test solution tostand at rest at a prescribed temperature for a prescribed duration(such as, for example, 90° C. and one hour) and thereafter assaying thetest solution for absorbency in the wavelength zone of the ultravioletlight (UV). The method for the determination of the degree of gelationwill be more specifically described in a working example to be citedherein below.

Then, the weight average molecular weight, Mw, of the (meth)acrylic acidtype polymer according to this invention is generally in the range of2000–20000, preferably in the range of 3000–15000, and more preferablyin the range of 4000–10000. When the weight average molecular weight isin this range, the aforementioned (meth)acrylic acid type polymer isenabled to manifest conspicuously and effectively various propertiessuch as dispersibility, chelating ability, and anti-gelling property.Thus, it can be applied more advantageously to such uses as adispersant, a descaling agent, and a detergent builder. If the weightaverage molecular weight of the (meth)acrylic acid type polymer fallsshort of 2000, the shortage will possibly prevent the dispersing abilityand the chelating ability from being manifested fully satisfactorily andrestrict the uses to be found for the polymer. Conversely, if the weightaverage molecular weight of the (meth)acrylic acid type polymer exceeds20000, the excess will transform the polymer to a high polymer andprevent the polymer from easily manifesting the satisfactory watersolubility and anti-gelling property. When the (meth)acrylic acid typepolymer (solid) obtained by purifying the aqueous solution containing a(meth)acrylic acid type polymer resulting from polymerization ismeasured for number average molecular weight by a proper method and whenthe aqueous solution containing a (meth)acrylic acid type polymerresulting from polymerization is measured for number average molecularweight, substantially no difference arises between the two measurements.In determining the value Q, therefore, it suffices to determine eitherof the weight average molecular weights.

The methods for determining the weight average molecular weight (Mw) andthe number average molecular weight (Mn) of the (meth)acrylic acid typepolymer will be described specifically in a working example to be citedherein below.

Then, the degree of dispersion (Mw/Mn) of the (meth)acrylic acid typepolymer according to this invention is in the range of 1.5–2.9,preferably in the range of 1.8–2.7, and more preferably in the range of2.0–2.5 when (1) the Mw falls short of 9000, depending on the magnitudeof Mw. If this degree of dispersion falls short of 1.5, the shortagewill complicate the synthesis of the polymer. Conversely, if the degreeof dispersion exceeds 2.9, the excess will possibly induce degradationof quality because of the decrease in the component which is effectivein fixing the quality and possibly prevent the (meth)acrylic acid typepolymer to acquire a fully satisfactory dispersing ability and impose arestriction on the uses to be found for the polymer. Then, the degree ofdispersion is in the range of 1.5–4.5, preferably in the range of2.0–4.0, and more preferably in the range of 2.5–3.5 when (2) the Mw isin the range of 9000–20000. In this case, if the degree of dispersionfalls short of 1.5, the shortage will result in complicating thesynthesis of the polymer. Conversely, if the degree of dispersionexceeds 4.0, the excess will possibly induce degradation of qualitybecause of a decrease in the component which is effective in governingthe quality.

The Ca-binding capacity (one sort of the chelating ability) of the(meth)acrylic acid type polymer according to this invention can bedecided in accordance with the Mw. When the Mw is in the range of3000–10000, for example, the Ca-binding capacity is not less than 235,preferably not less than 240. If the Ca-binding capacity falls short of235, the shortage will possibly prevent a detergent incorporating thepolymer therein from manifesting fully satisfactory detergency. The(meth)acrylic acid type copolymer of this invention which particularlyfulfills the value S representing the quantity of the sulfur elementintroduced and further preferably satisfies such necessary conditions asthe value R, the iron ion concentration, and the value Q and enjoys adecrease in the quantity of an impurity far excels the (meth)acrylicacid type polymer of this invention proposed formerly by the presentinventors in the Ca-binding capacity (chelating ability). Thus, it isenabled to manifest a decisively high decomposing and deterging power onthe dirt of perspiration and the dirt of mud adhering to clothing, i.e.the dirt containing a Ca component and the tap water containing Ca.

The hue of the (meth)acrylic acid type polymer according to thisinvention excels the existing PSA assuming a yellow t brown color interms of colorlessness and transparency. When general consumers(clients) are sizing up such products as detergents which are mostly ina white color, they often take into consideration even the hues of suchdetergents. In the light of the fact that the detergents which arecolorless and transparent excel those which assume a yellow color interms of commercial value, the polymer enjoying colorlessness andtransparency proves highly advantageous.

The range of the degree of neutralization of the (meth)acrylic acid typepolymer according to this invention ought not to be particularlyrestricted but may be properly adjusted to suit the purpose of use. Itis generally in the range of 1–100%, preferably in the range of 20–99%,and more preferably in the range of 50–95%.

The (meth)acrylic acid type polymer of this invention is preferred to bea polymer which is formed by polymerizing in an aqueous solution acomposition containing 50–100 mol % of (meth)acrylic acid and 0–50 mol %of a water-soluble monoethylenically unsaturated monomer capable ofcopolymerizing with the (meth)acrylic acid and consequently endowed withsuch necessary conditions as the aforementioned value S representing thequantity of the sulfur element introduced and further preferably thevalue R, the iron ion concentration, and the value Q. This polymer isfurther preferred to be a (meth)acrylic acid type polymer having such asulfur-containing group as a sulfonic group linked to the terminal or tothe main chain and having a value Q of less than 3.0 for theanti-gelling ability. Such a (meth)acrylic acid type polymer assatisfies these necessary conditions has such a sulfur-containing groupas a sulfonic group linked to the terminal or the side chain of thepolymer. Thus, this polymer exhibits a better anti-gelling property thanthe conventional polymer notwithstanding it has a large molecular weightas compared with the conventional polymer having an anti-gellingproperty. Further, since this polymer has a small impurity content, itcan form a water-soluble polymer of a low molecular weight which hasderived the maximum quality without sacrificing such prominentproperties as dispersibility, chelating ability, and anti-gellingproperty. This polymer, therefore, can be advantageously applied to suchuses as a dispersant, a descaling agent, and a detergent builder. The(meth)acrylic acid type polymer of this invention may be a polymerformed by polymerizing in an aqueous solution a composition containing50–100 mol % of (meth)acrylic acid and 0–50 mol % of a water-solublemonoethylenically unsaturated monomer capable of copolymerizing with the(meth)acrylic acid and consequently has such a sulfur-containing groupas a sulfonic group linked to the terminal or to the main chain and hasdeviated from the necessary condition that the aforementioned value Qrepresenting the anti-gelling ability be less than 3.0. The polymermanifests the operation and the effect of this invention so long as itsatisfies such necessary conditions as the aforementioned value Srepresenting the quantity of the sulfur element introduced, and morepreferably the value R, the iron ion concentration, and the value Q. The(meth)acrylic acid type polymers including the copolymers with suchmonomers as, for example, maleic acid, fumaric acid, itaconic acid,2-hydroxyethyl (meth)acrylic acid, and copolymers thereof which arecited in Sub-paragraph “Monomer (II)” described herein below areembraced by this invention so long as they satisfy such necessaryconditions as the aforementioned value S representing the quantity ofthe sulfur element introduced and further preferably the value R, theiron ion concentration, and the value Q.

The existing water-soluble polymers of low molecular weights which areused for dispersants and descaling agents are such that when theirweight average molecular weights exceed 1000, they have theiranti-gelling property exalt in accordance as their molecular weightsdecrease, namely as their weight average molecular weights approximateclosely to 1000. Meanwhile, their chelating ability is exalted inaccordance as the weight average molecular weights of the water-solublepolymers increase. The conventional water-soluble polymers, therefore,have incurred difficulty in satisfactorily improving the threeproperties, i.e. dispersibility, chelating ability, and anti-gellingproperty, all together.

In contrast thereto, the (meth)acrylic acid type polymer which is apolymer resulting from polymerizing in an aqueous solution theaforementioned monomer containing 50–100 mol % of (meth)acrylic acid and0–50 mol % of a water-soluble monoethylenically unsaturated monomercapable of copolymerizing with the (meth)acrylic acid and which isconsequently enabled to have such a sulfur-containing group as asulfonic group linked to the terminal or the main chain, allow a value Qof less than 3.0 for the anti-gelling ability, and satisfy theaforementioned value S representing the quantity of the sulfur elementintroduced has such a sulfur-containing group as a sulfonic groupintroduced to the terminal or the side chain of the polymer. Thispolymer preferably fulfills such necessary conditions as the value R andthe iron ion concentration. Such a (meth)acrylic acid type polymer asthis excels in the dispersing ability and the anti-gelling propertynotwithstanding the weight average molecular weight is comparativelylarge. Particularly, for the large weight average molecular weight, theanti-gelling property is highly satisfactory. The (meth)acrylic acidtype polymer which satisfies such necessary conditions as these,therefore, exhibits a high dispersing ability and an exceptionally fineanti-gelling property (refer to the value Q representing theanti-gelling ability shown in Table 11) besides manifesting thechelating ability of the same degree (refer to the Ca-binding capacityshown in Table 11) as the conventional (meth)acrylic acid type polymerwhich has an about equal weight average molecular weight.

As described above, the (meth)acrylic acid type polymer according tothis invention is preferred to have such a sulfur-containing group as asulfonic group linked to the terminal or the main chain and as wellpossess a high anti-gelling property. Owing to such sulfur-containinggroups as the terminal sulfonic group just mentioned, the polymer isenabled to enhance the dispersing ability and the chelating abilitythereof. Further, it is capable of manifesting a higher anti-gellingproperty. Thus, this (meth)acrylic acid type polymer is advantageouslyapplied to such uses as a dispersant for inorganic pigments, a descalingagent, and a detergent builder.

The necessary condition that the polymer formed by polymerizing in anaqueous solution the aforementioned monomer containing 50–100 mol % of(meth)acrylic acid and 0–50 mol % of a water-soluble monoethylenicallyunsaturated monomer capable of polymerizing with the (meth)acrylic acidhave such a sulfur-containing group as a sulfonic group linked to theterminal or the side chain and offer a value Q of less than 3.0 for theanti-gelling ability (of which the requirement regarding the value Q isas described above) will be described below in conjunction with themethod for the production of a (meth)acrylic acid type polymer.

The second aspect of this invention is directed toward a method for theproduction of a (meth)acrylic acid type polymer, characterized by usingas an initiator the combination of one or more species respectively of apersulfate and a bisulfite, wherein the bisulfite is used in aproportion in the range of 0.5–5 by mass ratio relative to the mass ofthe persulfate taken as 1, the total quantity of the persulfate and thebisulfite to be added to the reaction system of polymerization is in therange of 2–20 g per mol of the monomer to be polymerized, and thepolymerization temperature is in the range of 25–99° C.

By adding as an initiator not only a persulfate but also a bisulfite inproportions in the ranges mentioned above, it is made possible toprevent the produced (meth)acrylic acid type polymer from beingtransformed into an unnecessarily high polymer and attain efficientproduction of a polymer of a low molecular weight. Besides this benefit,the produced (meth)acrylic acid type polymer is capable of incorporatetherein such a sulfur-containing group as a sulfonic groupquantitatively, i.e. in such a quantity as permits the aforementionedvalue S representing the quantity of the sulfur element introduced tofall in the range specified above. The fact that such asulfur-containing group as a sulfonic group can be introducedquantitatively indicates that the persulfate and the bisulfite arefunctioning very satisfactorily as an initiator. Thus, the reactionsystem of polymerization does not require addition of an excessinitiator and allows a further decrease in the quantity of the initiatorto be added. As a result, it is made possible to repress the rise of thecost of production of the polymer and enhance the efficiency ofproduction. The produced (meth)acrylic acid type polymer, therefore, iscapable of repressing the aggregation with a metal salt of calcium, forexample, and acquiring a satisfactory anti-gelling property. Further, bycontrolling the quantity of the initiator to be added to the reactionsystem of polymerization and the polymerization temperature withincertain ranges, it is made possible to repress the generation of sulfurdioxide in a large quantity and allay the generation of an impurity aswell. Thus, the further enhancement of the quality can be realized, therise of the cost of production of the polymer can be repressed, and theefficiency of production can be exalted.

The monomer to be used in the method of production according to thisinvention does not need to be particularly restricted but has only tocomprise a monomer component capable of producing a (meth)acrylic acidtype polymer by polymerization. It is only required to contain at least(meth)acrylic acid (hereinafter referred to occasionally as monomer(I)). Optionally, it may contain a water-soluble monoethylenicallyunsaturated monomer capable of copolymerizing with (meth)acrylic acid(hereinafter referred to occasionally as monomer (II)) and/or othermonomer (hereinafter referred to occasionally as monomer (III)). Theterm “monomer” as used herein refers to what is formed of a monomercomponent and does not embrace a solvent, an initiator, and otheradditives which are other components to be used in the course ofpolymerization.

As concrete examples of the monomer (I) component, acrylic acid andmethacrylic acid may be cited. These monomers may be used either singlyor in combination. Preferably, acrylic acid alone or a mixture formed bymixing acrylic acid and methacrylic acid at a prescribed ratio.

The quantity of the monomer (I) to be incorporated in the aforementionedmonomer is generally in the range of 50–100 mol %, preferably in therange of 70–100 mol %, and more preferably in the range of 90–100 mol %based on the total quantity of the monomer. If the quantity of themonomer (I) to be incorporated falls short of 50 mol %, the shortagewill be at a disadvantage in preventing the chelating ability and theanti-gelling ability from being manifested as balanced harmoniously.Meanwhile, the upper limit of this quantity may be 100 mol %, namely themonomer may be formed wholly of (meth)acrylic acid. Further, whenacrylic acid and methacrylic acid are used in combination as the monomer(I), the quantity of the methacrylic acid to be incorporated generallyavoids exceeding 5 mol % and preferably falls in the range of 0.5–4 mol% and more preferably in the range of 1–3 mol %. If the quantity of themethacrylic acid to be incorporated exceeds 5 mol %, the excess willpossibly result in degrading the chelating ability.

The monomer (I) may be added to the solvent which will be specificallydescribed herein below preferably in the form of a solution (preferablyan aqueous solution) of the monomer (I) in water. When the monomer (I)is used as the solution (preferably aqueous solution), the concentrationthereof is generally in the range of 10–100 mass %, preferably in therange of 30–95 mass %, and more preferably in the range of 50–90 mass %.If the concentration of the monomer (I) in the solution falls short of10 mass %, the shortage will result in lowering the concentration of theproduct and complicating transportation and storage of the product. Theupper limit of this concentration ought not be particularly restricted.The concentration may be 100 mass % (namely wholly) of the monomer (I)(solution), i.e. the solution may be absolutely devoid of a solvent.

As concrete examples of the water-soluble monoethylenically unsaturatedmonomer which is capable of copolymerizing with (meth)acrylic acid, i.e.the aforementioned monomer (II), salts formed by partially neutralizingor completely neutralizing (meth)acrylic acid, i.e. the monomer (I),with such an alkali metal as sodium or potassium; salts formed bypartially or completely neutralizing the monomer (I) with either ammoniaor such an organic amine as monoethanol amine or triethanol amine; suchmonoethylenically unsaturated aliphatic monocarboxylic acids as crotonicacid and α-hydroxyacrylic acid; salts formed by partially or completelyneutralizing the aforementioned monoethylenically unsaturated aliphaticmonocarboxylic acid with an alkali metal; salts formed by partially orcompletely neutralizing the aforementioned monoethylenically unsaturatedaliphatic monocarboxylic acid with either ammonia or such an organicamine as monoethanol amine or triethanol amine; such monoethylenicallyunsaturated aliphatic dicarboxylic acids as maleic acid, fumaric acid,and itaconic acid; salts formed by partially or completely neutralizingthe aforementioned monoethylenically unsaturated aliphatic dicarboxylicacids; salts formed by partially or completely neutralizing theaforementioned monoethylenically unsaturated aliphatic dicarboxylicacids with either ammonia or such an organic amine as monoethanol amineor triethanol amine; such monoethylenically unsaturated monomerscontaining a sulfonic group as vinyl sulfonic acid, allyl sulfonic acid,and 3-alyloxy-3-hydroxypropane sulfonic acid; salts formed by partiallyor completely neutralizing the aforementioned monoethylenicallyunsaturated monomers with an alkali metal; salts formed by partially orcompletely neutralizing the aforementioned monoethylenically unsaturatedmonomers with either ammonia or such an organic amine as monoethanolamine or triethanol amine; and such unsaturated hydrocarbons containinga hydroxyl group as 3-methyl-2-buten-1-ol (occasionally referred tosimply as prenol) and 3-methyl-3-buten-1-ol (occasionally referred tosimply as isoprenol) may be cited, though not exclusively.

The monomer (II) may be properly selected from among the variouscompounds enumerated above, which may be used either singly or in theform of a combination of two or more members. Among other compoundscited above, one or more compounds selected from the group consisting ofunsaturated aliphatic dicarboxylic acids, unsaturated hydrocarbonscontaining a sulfonic group, and salts formed by partially or completelyneutralizing such compounds are preferably used because theyparticularly excel in chelating ability, dispersibility, andanti-gelling ability.

The quantity of the monomer (II) to be incorporated in the monomer isgenerally in the range of 0–50 mol %, preferably in the range of 0–30mol %, and more preferably in the range of 0–10 mol % based on the totalquantity of the monomer. If the quantity of the monomer (II) to beincorporated exceeds 50 mol %, the excess will possibly result indegrading the chelating ability. Meanwhile, since the monomer (II) is anarbitrary component, the lower limit of the quantity is 0 mol %. Thehomopolymer or the copolymer using the aforementioned monomer (I)component manifests the action and the effect of this invention fullysatisfactorily even in the absence of the use of the monomer (II).

The monomer (II) may be dissolved in a solvent which will bespecifically described herein below, preferably in water, and used inthe form of a solution (preferably aqueous solution) of the monomer(II). When the monomer (II) is used as the monomer (II) solution(preferably aqueous solution), the concentration thereof is in the rangeof 10–100 mass %, preferably in the range of 20–95 mass %, and morepreferably in the range of 30–90 mass %. If the concentration of themonomer (II) in this case falls short of 10 mass %, the shortage willresult in lowering the concentration of the product and complicatingtransportation and preservation of the product. Meanwhile, the upperlimit of this concentration ought not be particularly restricted. Theconcentration may be 100 mass % (namely wholly) of the monomer (II)(solution), i.e. the solution may be absolutely devoid of a solvent.

The monomer (III) other than the aforementioned monomers (I) and (II)does not need to be particularly restricted. As concrete examples of themonomer (III) usable herein, hydrophobic monomers, i.e. such(meth)acrylic esters as vinyl acetate, vinyl pyrrolidone, vinyl ethers,styrene, methyl (meth)acrylate, and ethyl (meth)acrylate may be cited.Such a monomer (III) as this may be properly selected from among thecompounds enumerated above, which may be used either singly or in theform of a combination of two or more members. When a hydrophobic monomeris used as the monomer (III), though it indeed excels in respect of theproperty of dispersing a hydrophobic compound, it possibly deterioratesthe anti-gelling property of the produced (meth)acrylic acid typepolymer. Thus, the quantity of this monomer (III) to be incorporatedmust be restricted in accordance with the kind of use to be selected.

When a hydrophobic monomer is incorporated as the monomer (III)mentioned above, the quantity of the monomer (III) component to beincorporated generally avoids exceeding 40 mol % and preferably falls inthe range of 0–20 mol % and more preferably in the range of 0–10 mol %based on the total quantity of the monomer. In other words, the quantityof the hydrophilic monomer combining the monomer (I) and the monomer(II) mentioned above (namely the hydrophilic monomer containing not lessthan 50 mol % of (meth)acrylic acid) to be incorporated generallyexceeds 60 mol % and preferably falls in the range of 80–100 mol % andmore preferably in the range of 90–100 mol % based on the total quantityof the monomer. If the quantity of the hydrophobic monomer of theaforementioned monomer (III) to be incorporated exceeds 40 mol % (namelywhen the quantity of the hydrophilic monomer combining the monomer (I)and the monomer (II) mentioned above to be incorporated falls short of60 mol %), the produced polymer of a low molecular weight acquires sosolubility in water as explained in U.S. Pat. No. 3,546,099. Further,the produced (meth)acrylic acid type polymer possibly entails anaddition to the value Q representing the anti-gelling ability andpossibly fails to acquire an excellent anti-gelling property.

The monomer (III) may be dissolved in a solvent which will bespecifically described herein below (preferably an organic solvent) andadded in the form of a solution of the monomer (III). The concentrationof the monomer (III) thus used in the form of the monomer (III) solutionis generally in the range of 10–100 mass %, preferably in the range of20–95 mass % and more preferably in the range of 30–90 mass %. If theconcentration of the monomer (III) solution falls short of 10 mass %,the shortage will result in lowering the concentration of the productand complicating transportation and storage of the product. Meanwhile,the upper limit of this concentration ought not be particularlyrestricted. The concentration may be 100 mass % (namely wholly) of themonomer (II) (solution), i.e. the solution may be absolutely devoid of asolvent.

The method of this invention prefers the monomer mentioned above to bepolymerized in an aqueous solution. This aqueous solution contains asolvent, an initiator, and other additives.

Here, the solvent to be used in the reaction system of polymerizationduring the polymerization of the monomer in the aqueous solution ispreferred to be such an aqueous solvent as water, alcohol, glycol,glycerin, or a polyethylene glycol. Water proves particularlypreferable. Such aqueous solvents may be used either singly or the formof a combination of two or more members. For the purpose of exalting thesolubility of the aforementioned monomer in such a solvent, an organicsolvent may be properly added to the aqueous solvent in a proportionincapable of exerting an adverse effect on the polymerization of themonomer.

Specifically, as the organic solvent, one or more members properlyselected from among lower alcohols such as methanol and ethanol; amidessuch as dimethyl formaldehyde; and ethers such as diethyl ether anddioxane may be used.

The quantity of the aforementioned solvent to be used is generally inthe range of 40–200 mass % and preferably in the range of 45–180 mass %and more preferably in the range of 50–150 mass % based on the totalquantity of the monomer. If the quantity of this solvent to be usedfalls short of 10 mass %, the shortage will result in heightening themolecular weight. Conversely, this quantity exceeds 200 mass %, theexcess will result in lowering the concentration of the produced(meth)acrylic acid type polymer and possibly necessitating the removalof the used solvent. The greater part or the whole of the solvent may beplaced in the reaction vessel during the initial stage ofpolymerization. Part of the solvent may be added (dropwise) suitablyinto the reaction system independently during the process ofpolymerization. Otherwise, the solvent may be properly added (dropwise)into the reaction system together with the monomer component, aninitiator component, and other additives in such a form as has thesecomponents dissolved in advance in the solvent.

The initiator to be used in the reaction system of polymerization duringthe polymerization of the aforementioned polymer in the aqueous solutionis preferred to be the combination of one or more species respectivelyof a persulfate and a bisulfite. By using this initiator, it is madepossible to introduce a sulfonic group quantitatively to the terminal orthe side chain, attain production of a water-soluble polymer of a lowmolecular weight excelling in anti-gelling property as well as indispersibility and chelating ability, and allow effective manifestationof the action and the effect of this invention. By adding a bisulfitebesides a persulfate to the system of initiator, it is made possible toprevent the produced polymer from being transformed into anunnecessarily high polymer and allow efficient production of the polymerof a low molecular weight.

As concrete examples of the aforementioned persulfate, sodiumpersulfate, potassium persulfate, and ammonium persulfate may be cited.Then as concrete examples of the bisulfite, sodium bisulfite, potassiumbisulfite, and ammonium bisulfite may be cited. A sulfite or apyrosulfite may be used in the place of such a bisulfite.

The ratio of addition of the persulfate and the bisulfite is such thatthe quantity of the quantity of the bisulfite is in the range of 0.5–5mass parts, preferably in the range of 1–4 mass parts, and morepreferably in the range of 2–3 mass parts based on one mass part of thepersulfate. If the quantity of the bisulfite based on 1 mass part of thepersulfate falls short of 0.5 mass part, the shortage will result inpreventing the effect of the bisulfite from being manifested fullysatisfactorily and, as a result, possibly disabling introduction of asulfonic group to the terminal of the polymer in a quantity satisfyingthe aforementioned value S representing the quantity of the sulfurelement introduced and further tending to add to the weight averagemolecular weight of the (meth)acrylic acid type polymer. Conversely, ifthe quantity of the bisulfite exceeds 5 mass parts based on one masspart of the persulfate, the excess will result in inducing such excesssupply (unnecessary consumption) of the bisulfite in the reaction systemof polymerization as prevents the effect of the bisulfite from beingproduced proportionately to the ratio of addition, consequently causingthe excess bisulfite to undergo decomposition in the reaction system ofpolymerization and entail generation of a large quantity of sulfurdioxide, forming an impurity in a large quantity in the (meth)acrylicacid type polymer, and eventually degrading the quality of the produced(meth)acrylic acid type polymer and inducing precipitation of animpurity during the preservation of the product at a low temperature.

The quantities of the persulfate and the bisulfite to be added as theinitiator are such that the total quantity of the persulfate and thebisulfite of the initiator is in the range of 2–20 g, preferably in therange of 4–15 g, more preferably in the range of 6–12 g, and still morepreferably in the range of 6–9 g, per mol of the monomer. In spite ofthe addition of the persulfate and the bisulfite in such smallquantities as these, this invention is enabled to allay remarkably thegeneration of sulfur dioxide and the occurrence of an impurity duringthe course of production, with the repression of the polymerizationtemperature to a low level as a contributive factor. As a result, it ismade possible to introduce such a sulfur-containing group as a sulfonicgroup to the terminal or the side chain of the produced (meth)acrylicacid type polymer in such a quantity as satisfies the value Srepresenting the quantity of the sulfur element introduced definedabove. It is further made possible to preclude the degradation of thequality of the produced (meth)acrylic acid type polymer and theprecipitation of an impurity during the preservation of the product at alow temperature. If the total quantity of the persulfate and thebisulfite of the initiator to be added falls short of 2 g, the shortagewill result in eventually increasing the molecular weight of theproduced polymer, possibly preventing such a sulfur-containing group asa sulfonic group from being introduced to the terminal of the produced(meth)acrylic acid type polymer in such a quantity as satisfies thevalue S representing the quantity of the sulfur element introduceddefined above, and tending to increase the weight average molecularweight of the polymer. Conversely, if the total quantity exceeds 20 g,the excess will be at a disadvantage in preventing the persulfate andthe bisulfite of the initiator from producing an effect proportionate tothe quantity of addition and exerting such adverse effects as degradingthe purity of the produced (meth)acrylic acid polymer.

The aforementioned persulfate which is one species of the initiator maybe dissolved in the aforementioned solvent, preferably water, and addedin the form of the persulfate solution (preferably aqueous solution).The concentration of the persulfate which is used in the form of thepersulfate solution (preferably aqueous solution) is in the range of1–35 mass %, preferably in the range of 5–35 mass %, and more preferablyin the range of 10–30 mass %. If the concentration of the persulfatefalls short of 1 mass %, the shortage will result in eventually loweringthe concentration and complicating transportation and storage of theproduct. Conversely, if the concentration of the persulfate exceeds 35mass %, the excess will possibly result in inducing precipitation of thepersulfate.

The bisulfite which is one species of the initiator may be dissolved inthe aforementioned solvent, preferably water, and added in the form ofthe bisulfite solution (preferably aqueous solution). The concentrationof the bisulfite which is used in the form of the bisulfite solution(preferably aqueous solution) is in the range of 10–40 mass %,preferably in the range of 20–40 mass %, and more preferably in therange of 30–40 mass %. If the concentration of the bisulfite falls shortof 10 mass %, the shortagewill result ineventually lowering theconcentration of the product and complicating transportation and storageof the product. Conversely, if the concentration of the bisulfiteexceeds 40 mass %, the excess will possibly result in inducingprecipitation of the bisulfite.

This invention does not exclude such a mode of embodiment as furtheruses other initiator (inclusive of a chain transfer agent). Such otherinitiator may be properly used, when necessary, in such a quantity asavoids exerting any adverse influence on the effect of this invention.In this invention, the aforementioned combination of a persulfate and abisulfite is advantageously used in the initiator system. The initiatordoes not need to be particularly limited to this combination. Thisinvention allows introduction of such a sulfur-containing group as asulfonic group in such a quantity as satisfies the value S definedabove. An initiator system which is capable of producing the polymer ofa low molecular weight by one-step polymerization can be used herein.

As concrete examples of the other initiator (inclusive of a chaintransfer agent), azo type compounds such as2,2′-azobis(2-amidinopropane) hydrochloride, 4,4′-azobis-4-cyanovalericacid, azobis-isobutylonitrile, and 2,2′-abobis(4-methoxy-2,4-dimethylvaleronitrile); organic peroxides such as benzoyl peroxide, lauroylperoxide, peracetic acid, di-t-butyl peroxide, and cumene hydroperoxide;and hydrogen peroxide may be cited.

Such an initiator as this may be likewise dissolved in theaforementioned solvent, preferably water, and used in the form of thesolution (preferably aqueous solution). The concentration of theinitiator which is used in the form of the solution (preferably aqueoussolution) has only to be in such a range as avoids impairing the effectof this invention. Generally, it is properly decided so as to equal tothe aforementioned concentration of the persulfate or bisulfitesolution.

As concerns the additive other than the initiator which can be used inthe reaction system of polymerization during the polymerization of theaforementioned monomer in the aqueous solution, a proper additive may beadded in such a quantity as avoids exerting an adverse effect on theoperation and the effect of this invention. For example, a heavy metalconcentration adjusting agent, an organic peroxide, hydrogen peroxide,and a metal salt are usable as such additives.

The aforementioned heavy metal concentration adjusting agent does notneed to be particularly restricted. A polyvalent metal compound orsimple substance may be used. As concrete examples of the heavy metalconcentration adjusting agent, water-soluble polyvalent metal salts suchas vanadium oxytrichloride, vanadium trichloride, vanadyl oxalate,vanadyl sulfate, vanadic anhydride, ammonium metavanadate, ammoniumsulfate hypovanadous [(NH₄)₂SO₄.VSO₄.6H₂O], ammonium sulfate vanadous[(NH₄)V(SO₄)₂.12H₂O], copper acetate (II), copper (II), copper bromide(II), copper (II) acetyl acetate, cupric ammonium chloride, copperammonium chloride, copper carbonate, copper chloride (II), coppercitrate (II), copper formate (II), copper hydroxide (II), coppernitrate, copper naphthenate, copper oleate (II), copper maleate, copperphosphate, copper sulfate (II), cuprous chloride, copper cyanide (I),copper iodide, copper oxide (I), copper thiocyanate, ironacetylacetonate, iron ammonium citrate, ferric ammonium oxalate, ironammonium sulfate, ferric ammonium sulfate, iron citrate, iron fumarate,iron maleate, ferrous lactate, ferric nitrate, iron pentacarbonyl,ferric phosphate, and ferric pyrophosphate; polyvalent metal oxides suchas vanadium pentoxide, copper oxide (I), ferrous oxide, and ferricoxide; polyvalent metal sulfides such as iron sulfide (III), ironsulfide (II), and copper sulfide; and copper powder and iron powder maybe cited.

For this invention, the heavy metal concentration of the produced(meth)acrylic acid type polymer is preferred to be in the range of0.05–10 ppm. It is, therefore, commendable to add properly theaforementioned heavy metal concentration adjusting agent in a properquantity. The present inventors have further found that when a reactionvessel obtained by giving to the inner wall of the existing reactionvessel made of steel or a copper-based alloy a glass lining treatmentexcelling in a corrosion-resisting property and containers and stirrersmade of stainless steel (SUS) are used, heavy metal ions, especiallyiron ions, are liquated (supplied) in a proper quantity defined abovefrom the SUS, the material of the containers and others into thereaction solution under the conditions of production of this invention.The supply of ions which is effected in this manner is advantageous interms of the effect vs cost. In the method of production according tothis invention, the use of such reaction devices as reaction vessels andstirrers which are made of SUS can manifest the same operation andeffect as the addition of the aforementioned heavy metal concentrationadjusting agent. Though the existing reaction vessel made of steel or acopper-based alloy poses no problem, it possibly induces liquation ofheavy metal ions in an excess concentration. The use of the existingreaction vessel proves uneconomical because the liquation of heavy metalions inevitably induces development of the color originating in theheavy metal and consequently necessitates an operation for removing theheavy metal ions. The reaction vessel which has been given the glasslining treatment likewise poses no problem and permits use of the heavymetal concentration adjusting agent as occasion demands.

The polymerization temperature during the polymerization of theaforementioned monomer is generally in the range of 25–99° C. Thispolymerization temperature is preferably not lower than 50° C. and morepreferably not lower than 70° C. The polymerization temperature ispreferably not higher than 95° C. and more preferably not higher than90° C. The polymerization may proceed even at a temperature lower than90° C. If the polymerization temperature falls short of 25° C., theshortage will result in increasing the molecular weight and adding tothe quantity of an impurity and unduly elongating the polymerizationtime and consequently degrading the productivity. Conversely, if thepolymerization temperature exceeds 99° C., the excess will result indecomposing the bisulfite of the initiator and emitting sulfur dioxidein a large quantity, consequently inducing dissolution of sulfur dioxidein the liquid phase and occurrence of an impurity after thepolymerization, further entailing discharge of sulfur dioxide from thesystem and necessitating a costly treatment for the recovery of thedischarged sulfur dioxide during the process of polymerization, and,because of the escape of the bisulfite of the initiator in the form ofsulfur dioxide, preventing the added initiator from fully satisfactorilymanifesting an effect proportionately to the quantity of addition andpreventing the molecular weight from being lowered as required.Incidentally, the term “polymerization temperature” as used herein meansthe temperature of the reaction solution in the reaction system.

The polymerization temperature does not need to be constantly retainedapproximately at a fixed level. It is permissible, for example, toinitiate the polymerization at normal room temperature (which may fallshort of 25° C., since a transient deviation of the polymerizationtemperature from the aforementioned range does not depart from the scopeof this invention), elevating the temperature in a propertemperature-elevating time (or temperature-increasing rate) till aprescribed temperature, and retain the prescribed temperaturethereafter. Otherwise, the duration of dropwise addition may be variedfor each of such components as the monomer and the initiator which areadded dropwise. As concerns the manner of dropwise addition, thetemperature may be varied (raised or lowered) along the course of timewithin the aforementioned temperature range during the process ofpolymerization. The manner of dropwise addition ought not beparticularly restricted but is only required to avoid impairing theoperation and the effect of this invention.

Particularly in the case of the method which initiates thepolymerization at normal room temperature (method of room temperatureinitiation), when the duration of 300 minutes is prescribed, forexample, the polymerization may be so performed as to reach the settemperature (which is only required to be within the range ofpolymerization temperature defined above, preferably 70–90° C. and morepreferably 80–90° C. or so) within a span of 120 minutes, preferably inthe range of 0–90 minutes and more preferably in the range of 0–60minutes and thereafter may be allowed to remain at such a settemperature as this till the polymerization is terminated. If theduration of temperature elevation deviates from the range mentionedabove, the deviation will possibly result in suffering the produced(meth)acrylic acid type polymer to grow to an unnecessarily highpolymer. The polymerization having its duration set at 300 minutes hasbeen described for example. When the polymerization has a different setduration, it is commendable to set such a duration of temperatureelevation as similarly proportionates the duration of temperatureelevation to the duration of the polymerization by consulting theforegoing example.

The pressure in the reaction system during the polymerization of theaforementioned monomer is not particularly restricted. Thepolymerization may proceed under normal pressure (atmospheric pressure),reduced pressure, or increased pressure, whichever may best suit theoccasion. For the purpose of preventing discharge of sulfur dioxideduring the process of polymerization and allowing a required decrease inthe molecular weight, it is commendable to perform the polymerizationunder normal pressure or under such an increased pressure as arises in asealed reaction system. When the polymerization is performed undernormal pressure (atmospheric pressure), the reaction system neithernecessitates addition of a pressing device or decompressing device norrequires use of a reaction vessel or piping adapted to resist pressure.The normal pressure (atmospheric pressure), therefore, proves preferablefrom the viewpoint of the cost of production. That is, the optimumpressure conditions may be set, depending on the purpose for which theproduced (meth)acrylic acid type polymer is used.

For the atmosphere in the reaction system, though air may be used in itsunmodified form, an inert gas may be used preferably. It is commendableto have the interior of the reaction system displaced with such an inertgas as nitrogen in advance of the start of the polymerization, forexample. Consequently, the gas forming the atmosphere in the reactionsystem (such as, for example, oxygen gas) is dissolved in the liquidphase and consequently allowed to function as a polymerizationinhibitor. As a result, it is made possible to prevent the persulfate asan initiator from being inactivated and reduced and allow a furtherdecrease in the molecular weight.

In the method of production according to this invention, thepolymerization of the aforementioned monomer is preferred to proceedunder an acidic condition. By using the acidic condition for thepolymerization, it is made possible to repress the rise of the viscosityof the aqueous solution in the reaction system of polymerization andpermit satisfactory production of a (meth)acrylic acid type polymer of alow molecular weight. It is further made possible to increase remarkablythe efficiency of production because the reaction of polymerization canbe made to proceed under the condition of a higher concentration thanthe level heretofore attained. Particularly, by lowering the degree ofneutralization during the course of polymerization to a level in therange of 1–25 mol %, it is made possible to heighten synergistically theeffect of decreasing the quantity of the aforementioned initiator andconsequently exalting remarkably the effect of decreasing the impurity.Further, it is preferable to have the pH of the reaction solution soadjusted in the process of polymerization as to fall in the range of 1–6at 25° C. By performing the reaction of polymerization under such anacidic condition as this, it is made possible to perform thepolymerization at a high concentration and in one step as well. It is,therefore, made possible to obviate the step of concentration which hasbeen possibly necessitated by the conventional method of production.Thus, the productivity of the (meth)acrylic acid type polymer can beremarkably enhanced and the rise of the cost of production can berepressed.

In the aforementioned acidic condition, the pH of the reaction solutionat 25° C. during the process of polymerization is in the range of 1–6,preferably in the range of 1–5 and more preferably in the range of 1–4.If this pH falls short of 1, the shortage will possibly result ininducing emission of sulfur dioxide and exposing the devices tocorrosion. Conversely, if this pH exceeds 6, the excess will result indegrading the efficiency of the bifulite and unduly increasing themolecular weight.

As concrete examples of the pH adjusting agent to be used for adjustingthe reaction solution in the process of polymerization to theaforementioned pH, hydroxides of alkali metals such as sodium hydroxideand potassium hydroxide, hydroxides of alkaline earth metals such ascalcium hydroxide and magnesium hydroxide; and organic amine salts suchas ammonia, monoethanol amine, and triethanol amine may be cited. ThesepH adjusting agents may be used either singly or in the form of acombination of two or more members. Among other pH adjusting agentsenumerated above, such hydroxides of alkali metals as sodium hydroxideand potassium hydroxide are preferable and sodium hydroxide isparticularly preferable. In the present specification, such a pHadjusting agent may be occasionally referred to simply as “a pHadjusting agent” or “a neutralizing agent.”

The degree of neutralization in the process of polymerization is in therange of 1–25 mol %. When the aforementioned monomer (I) alone forms themonomer to be used for the polymerization, the degree of neutralizationis preferably in the range of 2–15 mol % and more preferably in therange of 3–10 mol %. When the monomer to be used for the polymerizationincludes the monomer (II) in addition to the aforementioned monomer (I),it is permissible to have part or the whole of the monomer (II) added tothe reaction system during the initial stage of polymerization. In thiscase, the degree of neutralization in the process of polymerization ispreferably in the range of 1–25 mol % and more preferably in the rangeof 3–10 mol %. So long as the degree of neutralization in the process ofpolymerization falls in this range, the polymerization orcopolymerization can be effected most advantageously when theaforementioned monomer (I) alone is used and when the monomer (I) andthe monomer (II) are copolymerized. It is additionally made possible toproduce a polymer of a low molecular weight favorably without entailingan increase of the viscosity of the aqueous solution in the reactionsystem of polymerization. Moreover, since the reaction of polymerizationcan be made to proceed under the condition of a higher concentrationthan the level heretofore attained, the efficiency of production can beexalted remarkably. If the degree of neutralization in the process ofpolymerization falls short of 1 mol %, the shortage will possibly resultin increasing the quantity of sulfur dioxide to be emitted and adding tothe molecular weight. Conversely, if the degree of neutralization in theprocess of polymerization exceeds 25 mol %, the excess will result inpossibly degrading the efficiency of chain transfer of the bisulfite andincreasing the molecular weight. This excess will also result inconspicuously increasing the viscosity of the aqueous solution in thereaction system of polymerization in consequence of the advance of thepolymerization, consequently inducing an unnecessary addition to themolecular weight of the produced polymer and disabling the production ofa polymer of a low molecular weight, preventing the effect of thedecrease in the degree of neutralization from being manifested fullysatisfactorily, and rendering it difficult to attain a large decrease inthe impurity.

Here, the method for neutralization is not particularly restricted. Asthe neutralizing agent, such an alkaline monomer (II) component assodium (meth)acrylate may be utilized. It is also permissible to usesuch a hydroxide of alkali metal as sodium hydroxide instead.Optionally, they maybe used in combination. The neutralizing agent to beadded during the process of neutralization may be in a solid form or inthe form of an aqueous solution in a proper solvent, preferably water.When the aqueous solution is used, the concentration of this aqueoussolution is in the range of 10–60 mass %, preferably in the range of20–55 mass %, and more preferably in the range of 30–50 mass %. If theconcentration of the aqueous solution falls short of 20 mass %, theshortage will result in lowering the concentration of the product andcomplicating transportation and storage of the product. Conversely, ifthe concentration exceeds 60 mass %, the excess will result in possiblyinducing precipitation, heightening the viscosity, and consequentlycomplicating transfer of the solution.

In preparation for the polymerization, the monomer, the persulfate andthe bisulfite in the initiator system, and other additives are generallydissolved in advance in a proper solvent (preferably the same solvent asthe solvent used for the solutions intended for dropwise addition) toproduce a monomer solution, a persulfate solution, a bisulfite solution,and other additive solution. The polymerization is preferred to becontinued while these solutions are continuously added dropwise overprescribed durations of dropwise addition to the (aqueous) solvent(optionally adjusted to a prescribed temperature) placed in advance inthe reaction vessel. Further, part of the aqueous solvent may be addeddropwise afterward separately from the solvent placed in advance in thereaction vessel in the reaction system of polymerization during theinitial stage of polymerization (refer to Example 6 given in Table 1).The method of production of this invention, however, is not restrictedto the method described heretofore. As regards the method of dropwiseaddition, for example, the dropwise addition may be effectedcontinuously or intermittently as divided into several small fractions.Part or the whole of the monomer (II) may be placed in the reactionsystem during the initial stage of polymerization (namely part or thewhole of the monomer (II) may be regarded as added dropwise at once thenthe polymerization is initiated). Further, the speed of dropwiseaddition (the quantity of dropwise addition) of the monomer (II) may beconstantly fixed (fixed quantity) from the start through the completionof the dropwise addition or the speed of dropwise addition (quantity ofdropwise addition) maybe changed along the course of time, depending onthe polymerization temperature, for example. Instead of having all thecomponents of dropwise addition added dropwise at an equal rate, thetime for starting the dropwise addition and the time for completing thedropwise addition may be staggered from one to another of the individualcomponents of dropwise addition or the durations of dropwise additionassigned thereto may be shortened or elongated. Thus, the method ofproduction of this invention permits such a proper alteration as avoidsimpairing the operation and the effect of this invention. When theindividual components are added dropwise each in the form of a solution,the solutions for dropwise addition may be heated in advance to a levelequivalent to the polymerization temperature in the reaction system. Byso doing, the polymerization temperature, when required to be retainedat a fixed level, produces only small changes and permits easyadjustment.

When the monomers (I), (II), and/or (III) are copolymerized withmonomers A, B, and/or C which will be specifically described hereinbelow, the durations of dropwise addition of these individual monomersmay be controlled, depending on the polymerizing property of eachmonomer. When a monomer of a low polymerizing property is used, forexample, the duration of dropwise addition may be shortened. It is alsopermissible to have part or the whole of this monomer placed in advancein the relevant vessel within the reaction system.

Further, the bisulfite is such that the molecular weight thereof duringthe initial stage of polymerization largely affects the final molecularweight thereof. For the purpose of lowering the initial molecularweight, therefore, it is commendable to have a portion, 5–20 mass %, ofthe bisulfite or the solution thereof added (dropwise) to the reactionsystem within 60 minutes, preferably within 30 minutes, and morepreferably within 10 minutes after the start of polymerization. Thismeasure is particularly effective when the polymerization is initiatedat room temperature.

During the polymerization, it is more important to repress emission ofsulfur dioxide and prevent formation of an impurity by lowering thepolymerization temperature. For this purpose, the total duration ofdropwise addition in the process of polymerization is required to be solong as to fall in the range of 180–600 minutes, preferably in the rangeof 210–480 minutes, and more preferably in the range of 240–420 minutes.In view of the aforementioned problems encountered during the process ofproduction and in respect of encouraging the improvement of the qualityof the produced polymer, however, the elongation of the polymerizationtime may well be rated as a very significant measure. If the totalduration of dropwise addition falls short of 180 minutes, the shortagewill result in preventing the effect of the persulfate solution and thebisulfite solution added as an initiator system from being easilymanifested efficiently, rendering difficult the introduction of such asulfur-containing group as a sulfonic group to the terminal or the sidechain in such a manner as satisfies the value S representing thequantity of the sulfur element introduced, consequently disposing thepolymer to acquire a heightened weight average molecular weight,possibly inducing the presence of an excess initiator owing to thedropwise addition in a brief duration into the reaction system, andconsequently causing the excess initiator to decompose, emit sulfurdioxide, discharge it from the system, and give rise to an impurity. Theappreciation of the technical significance of confining thepolymerization temperature and the quantity of the initiator withinspecific low ranges, however, maybe regarded as precluding such problemsas described regarding the conventional technique from actuallyoccurring. This interpretation holds good even in the case of deviationsfrom various other polymerization conditions. Conversely, if the totalduration of dropwise addition exceeds 600 minutes, notwithstanding theproduced polymer enjoys an excellent quality because the emission ofsulfur dioxide is repressed, the excess will result in degrading theproductivity of the (meth)acrylic acid type polymer and possiblyrestriction the uses to be found for the produced polymer. The term“total duration of dropwise addition” as used herein refers to theduration from the time the dropwise addition of the first component fordropwise addition (not necessarily limited to one component) is startedtill the time the dropwise addition of the last component for dropwiseaddition (not necessarily limited to one component) is completed.

The duration of dropwise addition of the bisulfite or the solutionthereof among other components for dropwise addition during the processof polymerization is has the termination thereof advanced by an intervalin the range of 1–30 minutes, preferably in the range of 1–20 minutes,and more preferably 1–15 minutes from the point of termination of thedropwise addition of the monomer (I) or the solution thereof. By thismeasure, it is made possible to decrease the quantity of the bisulfiteafter completion of the polymerization and repress efficiently andeffectively the emission of sulfur dioxide and formation of an impurityfrom the bisulfite. Thus, the quantity of the impurity which occurs whenthe sulfur dioxide in the gas phase is dissolved in the liquid phaseafter completion of the polymerization can be markedly decreased. Whenthe bisulfite survives even after completion of the polymerization, itgives rise to an impurity and induces degradation of the quality of thepolymer and precipitation of an impurity during the preservation of theproduct at a low temperature. Thus, the initiator including thebisulfite is preferred to have been consumed till thorough eliminationby the time the polymerization is completed.

When the time for terminating the dropwise addition of the monomer (I)(solution) cannot be advanced by an interval of not less than one minutefrom the time for terminating the dropwise addition of the bisulfite(solution), the bisulfite possibly survives even after termination ofthe polymerization. The case of this nature embraces the case in whichthe termination of dropwise addition of the bisulfite or the solutionthereof and the termination of dropwise addition of the monomer (I) orthe solution thereof occur at the same time and the case in which thetermination of dropwise addition of the bisulfite (solution) occursafter the termination of dropwise addition of the monomer (I)(solution). In these cases, it is difficult to repress the emission ofsulfur dioxide and the formation of an impurity efficiently andeffectively and the surviving initiator possibly exerts an adverseeffect on the thermal stability of the produced polymer. Conversely,when the time for terminating the dropwise addition of the bisulfite orthe solution thereof precedes the time for terminating the dropwiseaddition of the monomer (I) (solution) by an interval exceeding 30minutes, the bisulfite has been used up by the time the polymerizationis terminated. This thorough consumption of the bisulfite possiblyincurs an increase of the molecular weight. Further, since the bisulfiteis dropwise added in a large quantity in a brief span of time during thecourse of the polymerization because the speed of the dropwise additionof the bisulfite is higher than the speed of the dropwise addition ofthe monomer (I) (solution), the impurity and the sulfur dioxide arepossibly generated in an increased quantity during this dropwiseaddition.

The time for terminating the dropwise addition of the persulfite(solution), among other components for dropwise addition, during theprocess of polymerization is delayed by an interval in the range of 1–30minutes, preferably in the range of 1–20 minutes, and more preferably inthe range of 1–15 minutes from the time for terminating the dropwiseaddition of the monomer (I) (solution). By this delay, it is madepossible to decrease the quantity of the monomer surviving aftercompletion of the polymerization and decrease markedly the impurityoriginating in the surviving monomer.

When the interval by which the time for terminating the dropwiseaddition of the persulfate (solution) is delayed from the time forterminating the dropwise addition of the monomer (I) (solution) fallsshort of 1 minute, this shortage will possibly result in inducingsurvival of the monomer component after the termination of thepolymerization. The case of this nature embraces the case in which thetermination of dropwise addition of the persulfate (solution) and thetermination of dropwise addition of the monomer (I) (solution) occur atthe same time and the case in which the termination of dropwise additionof the persulfate (solution) occurs after the termination of dropwiseaddition of the monomer (I) (solution). In these cases, the formation ofan impurity is efficiently and effectively repressed with difficulty.Conversely when the time for terminating the dropwise addition of thepersulfate (solution) is delayed by an interval exceeding 30 minutesafter the time for terminating the dropwise addition of the monomer (I)(solution), the persulfate or the product of decomposition thereofpossibly survives and forms an impurity after completion of thepolymerization.

The concentration of the solid component (namely the concentration ofthe solid component formed by the polymerization of the monomer) in theaqueous solution at the time that the dropwise addition of each of thecomponents is terminated and the reaction of polymerization in thereaction system of polymerization is terminated generally exceeds 35mass % and preferably falls in the range of 40–70 mass % and morepreferably in the range of 45–65 mass %. So long as the concentration ofthe solid component at the time for terminating the reaction ofpolymerization exceeds 35 mass %, the polymerization can be made toproceed at a high concentration and in one step as well. Thus, it ismade possible to obtain a (meth)acrylic acid type polymer of a lowmolecular weight with high efficiency. The step of concentration whichhas been necessary for the conventional method of production can beomitted, for example. Thus, the efficiency of the production can beexalted markedly. As a result, it is made possible to enhance theproductivity of the (meth)acrylic acid type polymer and repress the riseof the cost of production.

If the concentration of the solid component mentioned above falls shortof 35 mass %, the shortage will possibly result in preventing theproductivity of the (meth)acrylic acid type polymer from being markedlyenhanced as by rendering difficult the omission of the step ofconcentration, for example.

In the case of the conventional method, the increase of theconcentration of the solid component in the reaction system ofpolymerization has entailed such problems as inducing a remarkableincrease in the viscosity of the reaction solution in consequence of theadvance of the reaction of polymerization and consequently heighteningthe weight average molecular weight of the produced polymer markedly.When the reaction of polymerization is carried out on the acid side (thepH at 25° C. falling in the range of 1–6 and the degree ofneutralization falling in the range of 1–25 mol %), the rise of theviscosity of the reaction solution in consequence of the advance of thereaction of polymerization can be repressed. Thus, even when thereaction of polymerization is carried out under the condition of a highconcentration, the polymer of a low molecular weight can be obtained andthe efficiency of production of the polymer can be exalted markedly.

The expression “the point at which the reaction of polymerization isterminated” as used herein may be interpreted as the point at which thedropwise additions of all the components for dropwise addition areterminated and nevertheless is preferred to refer to the point by whichthe prescribed duration of aging (completion of polymerization) haselapsed thereafter.

The aforementioned duration of aging is generally in the range of 1–120minutes, preferably in the range of 5–60 minutes, and more preferably inthe range of 10–30 minutes. If the duration of aging falls short of 1minutes, the shortage will result in possibly inducing survival of themonomer component due to the insufficiency of agent and possiblyentailing formation of an impurity originating in the surviving monomerand degradation of the quality. Conversely, if the duration of agingexceeds 120 minutes, the excess will result in possibly coloring thepolymer solution. Besides, the polymerization has been already completedand further application of the polymerization temperature provesuneconomical.

During the process of aging, the polymerization temperature mentionedabove is applied because the aging proceeds during the reaction ofpolymerization and is embraced in the polymerization. The temperatureduring the process of aging may be retained at a fixed level (preferablythe temperature at the point at which the dropwise addition isterminated) or it may be changed along the course of time during theprocess of aging. The duration of the polymerization, therefore, refersto the sum of the aforementioned total duration of dropwise addition +the duration of aging and means the time which elapses from the pointfor starting the first dropwise addition to the point for terminatingthe aging.

Further, in the method for the production of a (meth)acrylic acid typepolymer according to this invention, the polymerization is performedunder the aforementioned acid condition (the pH of the reaction solutionin the process of polymerization falling in the range of 1–6 at 25° C.and the degree of neutralization in the process of polymerizationfalling in the range of 1–25 mol %). The degree of neutralization of theproduced (meth)acrylic acid type polymer (final degree ofneutralization), therefore, can be set in the prescribed range byproperly adding an appropriate alkali component by way of anafter-treatment, optionally after termination of the polymerization.

The aforementioned final degree of neutralization is variable with thekind of use and, therefore, ought not be particularly restricted. It maybe set at a level in a very wide range of 1–100 mol %. When the polymeris utilized as a detergent builder such as in a weakly acidic detergentwhich is claimed to be tender to the bare skin, for example, the polymermay be used in its original acid state instead of being neutralized inadvance. When it is used in a neutral detergent or an alkali detergent,it may be neutralized by way of an after-treatment with an alkalicomponent to a degree of neutralization of not less 90 mol % prior tothe use. Particularly when the polymer is used as an acid substance, thefinal degree of neutralization is preferably in the range of 1–75 mol %and more preferably in the range of 5–70 mol %. When the polymer is usedas a neutral or an alkali substance, the final degree of neutralizationis preferably in the range of 75–100 mol % and more preferably in therange of 85–99 mol %. If the final degree of neutralization of thepolymer being used as a neutral or an alkali substance exceeds 99 mol %,the excess will result in possibly coloring the aqueous solution of thepolymer.

As typical concrete examples of the aforementioned alkali component,hydroxides of alkali metals such as sodium hydroxide and potassiumhydroxide; hydroxides of alkaline earth metals such as calcium hydroxideand magnesium hydroxide; and organic amines such as ammonia, monoethanolamine, diethanol amine, and triethanol amine may be cited. The alkalicomponents enumerated above may be used either singly or in the form ofa combination of two or more members.

Incidentally, it is not impossible to set the final degree ofneutralization by subjecting a (meth)acrylic acid type polymer obtainedby the conventional method of complete neutralization or partialneutralization to a demineralizing treatment. In this case, however, theaddition of this demineralizing treatment may result in complicating theprocess of production and increasing the cost of production and, as aconsequence, possibly imposing a limit on the uses to be found.

When the polymer in its originally acid state is used without beingneutralized, since the reaction system is in an acid state as a matterof course, the atmosphere enclosed with the reaction system possiblysuffers noxious sulfur dioxide (SO₂ gas) to survive therein. In such acase as this, it is commendable to introduce such a peroxide as hydrogenperoxide into the system and decompose the sulfur dioxide or blow air ornitrogen gas into the system and expel the sulfur dioxide from thesystem.

The (meth)acrylic acid type polymer of this invention may be producedeither batchwise or continuously.

The method for the production of a (meth)acrylic acid type polymer ofthis invention, as described above, is characterized by using as aninitiator the combination of one or more species respectively of apersulfate and a bisulfite, wherein the bisulfite is used in aproportion in the range of 0.5–5 by mass ratio relative to the mass ofthe persulfate taken as 1, the total quantity of the persulfate and thebisulfite to be added to the reaction system of polymerization is in therange of 2–20 g per mol of the monomer, and the polymerizationtemperature is in the range of 25–99° C. Here, the polymerization ispreferred to be performed under an acid condition (the pH of thereaction solution in the process of polymerization falling in the rangeof 1–6 at 25° C. and the degree of neutralization during the course ofpolymerization falling in the range of 1–25 mol %), with the duration ofdropwise addition of each of the components for dropwise additioncontinuously adjusted in the meanwhile. Preferably, the concentration ofthe solid component of polymer at the time of terminating the reactionof polymerization is not less than 35 mass % and the weight averagemolecular weight of the produced polymer is in the range of 2000–20000.So long as the weight average molecular weight of the produced(meth)acrylic acid type polymer is in the range mentioned above, thequantity of the initiator to be added to the reaction system ofpolymerization can be markedly repressed. This fact is at an advantagein cutting cost, effectively and efficiently preventing the emission ofsulfur dioxide and the formation of an impurity during the process ofproduction, and consequently enabling a (meth)acrylic acid type polymercapable of conspicuously and effectively manifesting such properties ashigh dispersibility, a high chelating ability, and a high anti-gellingproperty on high levels to be produced efficiently. That is, a polymerwhich is usable advantageously for dispersants of inorganic pigments,descaling agents, and detergent builders can be produced in high qualityand at a low cost as well. Further, the reduction of the cost can beattained as by repressing markedly the increase in the quantity of theinitiator to be added to the reaction system of polymerization.

The uses found for the (meth)acrylic acid type polymer of this inventioninclude aqueous dispersants (inclusive of dispersants for pigments),descaling agents (scale repressing agents), detergent builders, anddetergents using the builders, for example. The uses do not need to belimited thereto but may embrace a wide variety of applications. Thepolymer may be applied to metal ion binding agents, thickening agents,and various binders, for example.

The aqueous dispersant of this invention is characterized by containinga (meth)acrylic acid type polymer (inclusive of the product ofpurification of (meth)acrylic acid type polymer as described above).Since the quantity of an impurity in the (meth)acrylic acid type polymeris markedly decreased, an aqueous dispersant of a low molecular weightwhich is capable of manifesting the outstanding dispersibility,chelating ability, and anti-gelling property owned inherently by the(meth)acrylic acid type polymer is provided by this invention. Thisinvention also provides an aqueous dispersant which possesses unusuallyhigh quality and performance and excels in stability and induces neitherdegradation of quality during a protracted storage nor precipitation ofan impurity during the preservation at a low temperature.

In the aqueous dispersant of this invention, the components of thecomposition other than the aforementioned (meth)acrylic acid typepolymer and their ratios in the composition are not particularlyrestricted. Such components and ratios in composition as mentioned abovemay be properly applied (utilized) within the ranges incapable ofimpairing the operation and the effect of this invention, based on thevarious components and their ratios of composition which are effectivelyapplied to the conventional aqueous dispersants.

The descaling agent of this invention is characterized by containing a(meth)acrylic acid type polymer (inclusive of the product ofpurification of (meth)acrylic acid type polymer as described above).Since the quantity of an impurity in the (meth)acrylic acid type polymeris markedly decreased, a water-soluble descaling agent of a lowmolecular weight which is capable of manifesting the outstandingdispersibility, chelating ability, and anti-gelling property ownedinherently by the (meth)acrylic acid type polymer is provided by thisinvention. This invention also provides a descaling agent whichpossesses unusually high quality and performance and excels in stabilityand induces neither degradation of quality during a protracted storagenor precipitation of an impurity during the preservation at a lowtemperature.

In the descaling agent of this invention, the components of thecomposition other than the aforementioned (meth)acrylic acid typepolymer and their ratios in the composition are not particularlyrestricted. Such components and ratios in composition as mentioned abovemay be properly applied (utilized) within the ranges incapable ofimpairing the operation and the effect of this invention, based on thevarious components and their ratios of composition which are effectivelyapplied to the conventional aqueous dispersants.

The detergent builder of this invention is characterized by containing a(meth)acrylic acid type polymer (inclusive of the product ofpurification of (meth)acrylic acid type polymer as described above).Since the quantity of an impurity in the (meth)acrylic acid type polymeris markedly decreased, a water-soluble detergent builder of a lowmolecular weight which is capable of manifesting the outstandingdispersibility, chelating ability, and anti-gelling property ownedinherently by the (meth)acrylic acid type polymer is provided by thisinvention. Thus, the detergent builder, when put to use, excels in theability to prevent the cleansed article from being defiled again. Thisinvention also provides a detergent builder which possesses unusuallyhigh quality and performance and excels in stability and induces neitherdegradation of quality during a protracted storage nor precipitation ofan impurity during the preservation at a low temperature.

In the detergent builder of this invention, the components of thecomposition other than the aforementioned (meth)acrylic acid typepolymer and their ratios in the composition are not particularlyrestricted. Such components and ratios in composition as mentioned abovemay be properly applied (utilized) within the ranges incapable ofimpairing the operation and the effect of this invention, based on thevarious components and their ratios of composition which are effectivelyapplied to the conventional detergent builders.

The detergent of this invention is characterized by containing a(meth)acrylic acid type polymer (inclusive of the product ofpurification of (meth)acrylic acid type polymer as described above).Since the quantity of an impurity in the (meth)acrylic acid type polymeris markedly decreased, a water-soluble detergent of a low molecularweight which is capable of manifesting the outstanding dispersibility,chelating ability, and anti-gelling property owned inherently by the(meth)acrylic acid type polymer is provided by this invention. Thisinvention also provides a detergent which possesses unusually highquality and performance and excels in stability and induces neitherdegradation of quality during a protracted storage nor precipitation ofan impurity during the preservation at a low temperature.

The detergent of this invention is preferred to contain a (meth)acrylicacid type polymer of this invention in a proportion in the range of 1–20mass % based on the total mass of the detergent and a surfactant in aproportion in the range of 5–70 mass % based on the total mass of thedetergent. Optionally, it may incorporate an enzyme therein in aproportion of not more than 5 mass %.

If the proportion of the (meth)acrylic acid type polymer incorporated inthe detergent falls short of 1 mass %, the shortage will result inpreventing the effect of the addition from being manifested as expected.If this proportion exceeds 20 mass %, the excess will result inpreventing the effect of the addition from being linked with theenhancement of the deterging power and eventually jeopardizing economy.If the quantity of the surfactant which is a main component of thedetergent deviates from the aforementioned range, the deviation willresult in upsetting the balance of the surfactant with the othercomponents and possibly exerting an adverse effect on the detergingpower of the detergent. The incorporation of the enzyme contributes tothe enhancement of the deterging power. If the quantity of the enzyme soincorporated exceeds 5 mass %, however, the excess will result inpreventing the effect of the addition from being manifested andeventually jeopardizing economy.

The surfactant to be used herein may be at least one member selectedfrom the group consisting of anionic surfactants, nonionic surfactants,amphoteric surfactants, and cationic surfactants. The anionic surfactantis not particularly restricted. As concrete examples of the anionicsurfactant which can be used herein, alkyl benzene sulfonates, alkyl oralkenyl ether sulfates, alkyl or alkenyl sulfates, α-olefin sulfonates,α-sulfo-fatty acids or esters, alkane sulfonates, saturated orunsaturated fatty acid salts, alkyl or alkenyl ether carboxylates, aminoacid type surfactants, N-acylamino acid type surfactants, and alkyl oralkenyl phosphoric esters or salts thereof may be cited.

The non-ionic surfactant is not particularly restricted. As concreteexamples of the non-ionic surfactant which is used herein,polyoxyalkylene alkyl or alkenyl ethers, polyoxyethylene alkylphenylethers, higher fatty acid alkanol amides or alkylene oxide adductsthereof, sucrose fatty acid esters, alkyl glycosides, fatty acidglycerin monoesters, and alkyl amine oxides may be cited.

The amphoteric surfactant is not particularly restricted. Carboxyl typeor sulfobetain type amphoteric surfactants are usable herein.

The cationic surfactant is not particularly restricted. Quaternaryammonium salts, for example, are usable herein.

As the enzyme to be incorporated in the detergent in this invention,proteases, lipases, and cellulases are usable herein.

Further, the detergent of this invention, when necessary, mayincorporate therein such components as known alkali builders, chelatebuilders, reattachment-preventing agents, soil release agents, colortransfer preventing agents, softening agents, fluorescent agents,bleaching agents, bleaching auxiliaries, and perfumed which are inpopular use in detergents. Zeolite may be also incorporated.

As the alkali builder, silicates, carbonates, and sulfates can be used.As the chelate builder, diglycolic acid, oxycarboxylates, EDTA (ethylenediamine tetraacetic acid), DTPA (diethylene triamine pentacetic acid),and citric acid may be optionally used. Otherwise, known polycarboxylicacid type polymers may be used in a proportion incapable of impairingthe effect of this invention.

The manner of incorporating the aforementioned (meth)acrylic acid typepolymer in the detergent of this invention is decided in accordance withthe form in which the detergent is marketed (such as, for example, aliquid state or a solid state) and ought not be particularly restricted.The polymer obtained in the form of an aqueous solution after thepolymerization may be incorporated in the unmodified form in thedetergent. Otherwise, the polymer in the form of an aqueous solution maybe treated to distill the water content to a certain extent andincorporated in the concentrated state in the detergent. Alternatively,the polymer which has been hardened to dryness may be incorporated inthe detergent.

The detergent mentioned above embraces detergents such as bleachingdetergents having one function of the component thereof enriched whichare used exclusively for specific purposes besides synthetic detergentsfor household use, industrial detergents directed toward textileindustry and other industries, and hard facial detergents.

The third aspect of this invention is directed toward an unsaturatedpolyalkylene glycol type copolymer, wherein the copolymer is produced bycopolymerizing a (meth)acrylic acid type monomer A and an unsaturatedpolyalkylene glycol type monomer B, the copolymer possesses sulfuroxygen acid at the terminal thereof, and the value S representing thequantity of the sulfur element introduced which is defined by theformula, S=(quantity of S contained in the polymer)/(total quantity ofS)×100, is not less than 3. The unsaturated polyalkylene glycol typecopolymer is produced by polymerizing a (meth)acrylic acid type monomerA and an unsaturated polyalkylene glycol type monomer B in an aqueoussolution. Optionally, a monoethylenically unsaturated monomer C which iscapable of copolymerizing with the monomer A and the monomer B mayparticipate in the copolymerization. The unsaturated polyalkylene glycoltype copolymer of this invention is a water-soluble polymer of a lowmolecular weight which is endowed at the terminal thereof with a sulfuroxygen acid and is excellent in anti-gelling property as well as indispersibility and chelating ability. The requirement that theunsaturated polyalkylene glycol type copolymer have a value S of notless than 3 for S, the quantity of the sulfur element introduced, can befulfilled by controlling the polymerization temperature and the degreeof neutralization in the respectively prescribed ranges during thecourse of production. By this control, it is made possible to repressemission of sulfur dioxide in a large quantity and formation of animpurity. The unsaturated polyalkylene glycol type copolymer having avalue S of not less than 3, the quantity of the sulfur elementintroduced which is obtained through such a process of production asthis has a very small impurity content and has the degradation ofquality due to the impurity repressed to a markedly low level. Thiscopolymer, by further having the precipitation of an impurity during thepreservation thereof in the form of an aqueous solution at a lowtemperature repressed to a markedly low level, is colorless andtransparent and excellent in hue as compared with the conventionalunsaturated polyalkylene glycol type copolymer. Thus, the furtherenhancement of the quality of this copolymer can be realized.

The term “sulfur oxygen acid” as used in this specification refers to anacidic group containing sulfur atoms and oxygen atoms and salts thereof.As concrete examples of the sulfur oxygen acid, groups derived fromsulfonic acid, sulfuric acid, persulfuric acid, and sulfurous acid;salts formed by partially neutralizing or completely neutralizing suchacid groups with an alkali metal; and salts formed by partiallyneutralizing or completely neutralizing such acid groups with eitherammonia or such an organic amine as monoethanol amine or triethanolamine may be cited.

The value S, the quantity of the sulfur element introduced, in theunsaturated polyalkylene glycol type copolymer exceeds 3 and preferablyfalls in the range of 3–50, and more preferably in the range of 3–30.The fact that the value S, the quantity of the sulfur elementintroduced, falls short of 3 means that the quantity of the initiatorused in the polymerization was more than necessary. This shortage,therefore, will result in preventing the formation of an impurity andthe emission of sulfur dioxide from being effectively repressed andpossibly inducing degradation of quality and precipitation of animpurity during the preservation of the copolymer at a low temperature.Meanwhile, the upper limit of the value S, the quantity of the sulfurelement introduced, ought not be particularly restricted.

The expression “the quantity of S contained in a polymer” as used in thedefinition of the value S, the aforementioned quantity of the sulfurelement introduced refers to the quantity of S, which is contained inthe unsaturated polyalkylene glycol type copolymer. Specifically, itrefers to the quantity of S contained in a high polymer component formedof an unsaturated polyalkylene glycol type copolymer which remains afterremoving such low molecular components as an impurity and an initiatorfragment from an aqueous solution formed by adjusting the solidcomponent concentration of an unsaturated polyalkylene glycol typecopolymer obtained by polymerization in accordance with the method ofdialysis explained in a working example cited herein below. In otherwords, it may be regarded as indicating the quantity of S, which isintroduced as such a sulfur-containing group as a sulfonic group intothe terminal or the side chain of the unsaturated polyalkylene glycoltype copolymer. It is logically inferred that the proportion of the Scomponent contained in the used initiator which is suitably incorporatedinto the unsaturated polyalkylene glycol type copolymer in consequenceof the reaction of polymerization increases in accordance as the valueS, the quantity of the sulfur element introduced, increases. The term“total quantity of S” used in the definition of the aforementioned valueS, the quantity of the sulfur element introduced, refers to the quantityof the whole S contained in the phase in which the unsaturatedpolyalkylene glycol type copolymer is present. The reason for not-usingthe quantity of S in the raw material used for the polymerization fromthe total quantity of S is that the quantity of S (sulfur component)which has been discharged out of the system as sulfur dioxide is absentfrom the aqueous solution of the unsaturated polyalkylene glycol typecopolymer and has no possibility of being precipitated as anS-containing impurity during the preservation at a low temperature.

The term “unsaturated polyalkylene glycol type copolymer” as used in thepresent invention refers to a comprehensive concept covering an aqueoussolution containing an unsaturated polyalkylene glycol type copolymerobtained by polymerization, the aforementioned aqueous solution havingsuch an aqueous solvent as water added thereto or removed therefrom in aproper quantity for the purpose of adjusting a solid contentconcentration, a solid substance obtained by depriving the aqueoussolution of the aqueous solvent and drying the residue, an unsaturatedpolyalkylene glycol type copolymer formed by purifying an aqueoussolution containing an unsaturated polyalkylene glycol type copolymerobtained by polymerization by suitably depriving the aqueous solution ofan impurity, the aqueous solution having an aqueous solvent addedthereto or removed therefrom for the purpose of adjusting a solidcontent concentration, an unsaturated polyalkylene glycol type copolymertransformed into a solid substance by drying, and an unsaturatedpolyalkylene glycol type copolymer obtained by polymerization andoptionally having proper additives such as, for example, preservationstabilizers (such as absorbent for ultraviolet light and antioxidant),coloring agents, antistatic agents, slip additives, fillers, flameretardants, and foaming agents incorporated therein in proportionsincapable of adversely affecting the quality of the copolymer. Theunsaturated polyalkylene glycol type copolymer of this invention,therefore, embraces a substance formed exclusively of a purifiedunsaturated polyalkylene glycol type copolymer. Thus, the unsaturatedpolyalkylene glycol type copolymer of this invention has only to satisfythe aforementioned value S representing the quantity of the sulfurelement introduced and ought to be interpreted in the broadest possiblesense without reference to the designation. It ought not to beinterpreted (restricted) narrowly as the solid component of anunsaturated polyalkylene glycol type copolymer or the aqueous solutionthereof. From the viewpoint of simplifying the process of production, itis commendable to utilize the aqueous solution containing theunsaturated polyalkylene glycol type copolymer obtained bypolymerization directly as a dispersant, a descaling agent, and adetergent builder, for example. From the view point of lowering the costof transportation, it is commendable to transport the copolymer in theform of a solid substance instead of such a bulky form of an aqueoussolution and optionally transform the solid substance into an aqueoussolution when the copolymer is compounded as a dispersant, a descalingagent, or a detergent builder, for example. From the viewpoint ofstabilizing the product in quality and stabilizing the preservation ofthe product, it is commendable to reduce the aqueous solution containingan unsaturated polyalkylene glycol type copolymer obtained bypolymerization to a finished product by depriving the aqueous solutionof an impurity. Thus, the copolymer may be suitably endowed with such ashape and a composition as befit the purpose of use. That is, theunsaturated polyalkylene glycol type copolymer does not need to beparticularly restricted on account of shape and composition but has onlyto be such that the copolymer obtained by polymerization fulfills therequirement that the value S representing the quantity of the sulfurelement introduced determined by the analysis of a prescribed method(specifically described in a working example hereinafter) be not lessthan 3.

The unsaturated polyalkylene glycol type copolymer according to thisinvention has a hue (value b) of not more than 2, preferably not morethan 1.5. The unsaturated polyalkylene glycol type copolymer of thisinvention is colorless and transparent as compared with the unsaturatedpolyalkylene glycol type copolymer of the conventional technique whichassumes a yellow-brown color. When general consumers (clients) aresizing up such products as detergents which are mostly in a white color,they often take into consideration even the hues of such detergents. Inthe light of the fact that the detergents which are colorless andtransparent excel those which assume a yellow color in terms ofcommercial value, the copolymer enjoying colorlessness and transparencyproves highly advantageous.

The unsaturated polyalkylene glycol type copolymer according to thisinvention is preferred to fulfill the requirement that the degree ofgelation, q, described specifically in a working example cited hereinbelow be not more than 0.1 when the Ca-binding capacity describedspecifically in a working example cited herein below is not less than200, besides satisfying the aforementioned value S, the quantity of thesulfur element introduced. When the Ca-binding capacity falls short of200, the value Q=(Ca-binding capacity)²/degree of gelation q/10⁵ ispreferred to be not less than 30. Heretofore, a polymer having ananti-gelling property used to have a particularly low molecular weightamong other polymers of low molecular weights. That is, for the purposeof obtaining a suitable anti-gelling property, it has been necessary todecrease further the molecular weight of a polymer already having a lowmolecular weight. In a polymer having an unduly small molecular weight,however, it is difficult to introduce such a sulfur-containing group asa sulfonic group quantitatively to the terminal or side chain of thepolymer, specifically in such a quantity as satisfies the value S, theaforementioned quantity of the sulfur element introduced. Thus, thispolymer has been unable to manifest the dispersing ability and thedescaling ability fully satisfactorily and therefore has been unsuitablefor such uses as a dispersant, a descaling agent, and a detergentbuilder. In contrast thereto, the unsaturated polyalkylene glycol typecopolymer according to this invention has such a sulfur-containing groupas a sulfonic group introduced quantitatively to the terminal or sidechain of the polymer, specifically in such a quantity as satisfies thevalue S, the aforementioned quantity of the sulfur element introduced.Optionally, it is enabled to satisfy the aforementioned value q or Q.Thus, the unsaturated polyalkylene glycol type copolymer mentioned aboveis capable of exhibiting a satisfactory anti-gelling property despiteits large molecular weight as compared with the conventional polymerhaving an anti-gelling property. So long as the aforementioned value Sand the value Q representing the anti-gelling ability as well fall inthe aforementioned ranges, the unsaturated polyalkylene glycol typecopolymer, when applied to such uses as an aqueous dispersant, adescaling agent, or a detergent builder, is enabled to repress its owntrend toward gelation and manifest highly satisfactory anti-gellingproperty and Ca-binding capacity. Thus, the copolymer can be suitablyapplied to such uses as an aqueous dispersant, a descaling agent, or adetergent builder. Since this copolymer is enabled to repress its owntrend toward gelation under the environment of use in its original formand further under the environment of preservation thereof in a formmixed (compounded) with other components, the product using thiscopolymer can realize further exaltation of the performance and furtherstabilization of the quality thereof.

When the Ca-binding capacity exceeds 200, the value q representing thedegree of gelation is less than 0.1, preferably less than 0.095. Whenthe Ca-binding capacity is less than 200, the value Q representing theanti-gelling ability is not less than 30, preferably not less than 35,and more preferably not less than 40. If the value q is not less than0.1 or if the value Q is not more than 30, the uses found for thecopolymer will be possibly restricted because of the insufficiency ofthe anti-gelling ability. The lower limit of the value q or the upperlimit of the value Q is not particularly restricted.

For the determination of the aforementioned “degree of gelation, q,” theknown method for determining the degree of gelation of an unsaturatedpolyalkylene glycol type copolymer may be suitably used. A testsolution, for example, is prepared by adding a low-concentration aqueoussolution (having a solid component concentration of 1 mass %, forexample) of the unsaturated polyalkylene glycol type copolymer accordingto this invention and an aqueous calcium chloride solution together in abuffer solution and mixing them altogether. The degree of gelation canbe determined by allowing this test solution to stand at rest at aprescribed temperature for a prescribed duration (such as, for example,90° C. and 1 hour) and testing the test solution for absorbency in thewave range of ultraviolet light (UV). A more specific method for thedetermination of the degree of gelation, q or the Ca-binding capacitywill be described in a working example to be cited herein below.

The weight average molecular weight Mw of the unsaturated polyalkyleneglycol type copolymer according to this invention is in the range of2000–100000, preferably in the range of 3000–50000, and more preferablyin the range of 4000–20000. When the weight average molecular weight isin this range, the unsaturated polyalkylene glycol type copolymer iscapable of conspicuously and effectively manifesting various propertiessuch as a dispersing ability, a chelating ability, and an anti-gellingproperty. Thus, the copolymer can be applied more suitably to such usesas a dispersant, a descaling agent, and a detergent builder. If theweight average molecular weight of the unsaturated polyalkylene glycoltype copolymer falls short of 2000, the shortage will result in possiblypreventing the dispersing ability and the chelating ability from beingsatisfactorily manifested and imposing a restriction on the uses foundtherefor. Conversely, if the weight average molecular weight of theunsaturated polyalkylene glycol type copolymer exceeds 100000, theexcess will result in imparting a higher molecular weight to thecopolymer and consequently preventing the satisfactory water solubilityand anti-gelling property from being manifested. The weight averagemolecular weight found for an unsaturated polyalkylene glycol typecopolymer obtained by purifying by a proper method an aqueous solutioncontaining an unsaturated polyalkylene glycol type copolymer resultingfrom polymerization and the weight average molecular weight found for anaqueous solution containing an unsaturated polyalkylene glycol typecopolymer resulting from polymerization show practically no difference.Therefore, it suffices to determine the weight average molecular weightof either an unsaturated polyalkylene glycol type copolymer or anaqueous solution thereof.

The methods for determining the weight average molecular weight (Mw) andthe number average molecular weight (Mn) of an unsaturated polyalkyleneglycol type copolymer or an aqueous solution thereof will be describedin a working example to be cited herein below.

The degree of dispersion (Mw/Mn) of the unsaturated polyalkylene glycoltype copolymer according to this invention, though variable with Mw, isin the range of 1.5–2.9, preferably in the range of 1.8–2.7, and morepreferably in the range of 2.0–2.5 when (1) Mw is less than 9000. Inthis case, if the degree of dispersion falls short of 1.5, the shortagewill result in complicating synthesis. Conversely if the degree ofdispersion exceeds 2.9, the excess will result in decreasing thecomponents effective in performance, consequently inducing a degradationof performance, possibly preventing the unsaturated polyalkylene glycoltype copolymer from exhibiting a sufficient dispersing ability, andimposing a restriction on the uses. The degree of dispersion is in therange of 1.5–4.5, preferably in the range of 2.0–4.0, and morepreferably in the range of 2.5–3.5 (2) when the Mw is in the range of9000–20000. In this case, if the degree of dispersion falls short of1.5, the shortage will result in complicating synthesis. Conversely, ifthe degree of dispersion exceeds 4.0, the excess will result indecreasing components effective in performance and possibly inducing adecline of performance.

The Ca-binding capacity (one form of the chelating ability) of theunsaturated polyalkylene glycol type copolymer according to thisinvention can be decided in accordance with the Mw and the compositionof the unsaturated polyalkylene glycol type copolymer. When the Mw is inthe range of 5000–10000 and the copolymer is composed of 80 mass % of a(meth)acrylic acid type monomer and 20 mass % of an unsaturatedpolyalkylene glycol type monomer, the Ca-binding capacity is not lessthan 160, preferably not less than 180, and more preferably not lessthan 200. If the Ca-binding capacity falls short of 160, the shortagewill result in possibly preventing the copolymer from producing asufficient deterging power. The unsaturated polyalkylene glycol typecopolymer of this invention which fulfills the aforementioned value Srepresenting the quantity of the sulfur element introduced andpreferably further satisfies the requirement concerning the value q andthe value Q excels conspicuously the unsaturated polyalkylene glycoltype copolymer of the invention formerly proposed by the presentinventors conspicuously in the Ca-binding capacity (the chelatingability) (refer to Table 20 given in a working example). It is,therefore, at an advantage in manifesting an unusually high decomposingand deterging power on dirt of perspiration and dirt of soil adhering toclothing and on dirt containing a Ca component, and a tap watercontaining Ca.

The range of the degree of neutralization of the unsaturatedpolyalkylene glycol type copolymer according to this invention ought notbe particularly restricted but may be properly adjusted so as to suitthe purpose of use. It is 1–100%, preferably 20–99 %, and morepreferably 50–95%.

The unsaturated polyalkylene glycol type copolymer of this inventionfulfills the aforementioned requirement concerning the aforementionedvalue S representing the quantity of the sulfur element introduced andcan be obtained by polymerizing a composition containing 30–99 mass % ofa (meth)acrylic acid type monomer and 1–70 mass % of an unsaturatedpolyalkylene glycol type monomer in an aqueous solution. The copolymer,when necessary, may additionally use 0–60 mass % of a water-solublemonoethylenically unsaturated monomer capable of copolymerizing themonomers mentioned above. It is provided, however, that the total mass %of a (meth)acrylic acid type monomer, an unsaturated polyalkylene glycoltype monomer, and a water-soluble monoethylenically unsaturated monomercopolymerizable with the monomers is 100. The unsaturated polyalkyleneglycol type copolymer of this invention is preferred to contain anunsaturated polyalkylene glycol type copolymer which has such asulfur-containing group as a sulfonic group linked to the terminal orthe main chain thereof. The unsaturated polyalkylene glycol typecopolymer which satisfies such necessary requirements as these isfurnished at the terminal or the side chain of the polymer with such asulfur-containing group as a sulfonic group. Thus, the polymer exhibitsa better anti-gelling property than the conventional polymer mentionedabove in spite of its large molecular weight as compared with theconventional polymer possessing an anti-gelling property. Further, sincethe polymer has a small impurity content, it can form an excellentwater-soluble polymer of a low molecular weight which has derived to themaximum such a high performance as a dispersibility, chelating ability,and anti-gelling property inherently owned by the polymer withoutsacrificing the quality. Thus, the polymer can be suitably applied tosuch uses as a dispersant, a descaling agent, and a detergent builder.The unsaturated polyalkylene glycol type copolymer of this invention isa polymer obtained by polymerizing a composition containing 30–99 mass %of a (meth)acrylic acid type monomer and 1–70 mass % of an unsaturatedpolyalkylene glycol type monomer in an aqueous solution and may not befurnished at the terminal or the main chain thereof with such asulfur-containing group as a sulfonic group. So long as the copolymersatisfies the necessary requirement of the aforementioned value Srepresenting the quantity of the sulfur element introduced, it manifeststhe operation and the effect of this invention. The aqueous solutions ofsuch unsaturated polyalkylene glycol type copolymers as copolymers ofmaleic acid, fumaric acid, itaconic acid, 2-hydroxyethyl (meth)acrylicacid, and copolymers thereof with monomers cited as Monomer C which willbe specifically described herein below are also embraced by thisinvention when they satisfy the aforementioned necessary conditionsregarding the aforementioned value S representing the quantity of thesulfur element introduced.

In the existing water-soluble polymer of a low molecular weight which isused for a dispersant and a descaling agent, when the weight averagemolecular weight is not less than 1000, the anti-gelling property isheightened in accordance as the molecular weight of the water-solublepolymer decreases, namely the weight average molecular weightapproximates more closely to 1000. The chelating ability is heightenedin accordance as the weight average molecular weight of thewater-soluble polymer increases. Thus, the conventional water-solublepolymer has incurred difficulty in satisfactorily enhancing all thethree properties, i.e. dispersibility, chelating ability, andanti-gelling property.

In contrast, the unsaturated polyalkylene glycol type copolymer which isa polymer formed by polymerizing the aforementioned monomer containing30–99 mass % of (meth)acrylic acid type monomer and 1–70 mass % of anunsaturated polyalkylene glycol type monomer and optionally 0–60 mass %of a water-soluble monoethylenically unsaturated monomer in an aqueoussolution and which has such a sulfur-containing group as a sulfonicgroup linked to the terminal or the main chain thereof and fulfills thenecessary conditions regarding the aforementioned value S representingthe quantity of the sulfur element introduced excels in dispersibilityand anti-gelling property in spite of its comparatively large weightaverage molecular weight because it has such a sulfur-containing groupas a sulfonic group linked to the terminal or the side chain of thepolymer. For the large weight average molecular weight, the anti-gellingproperty is highly satisfactory relatively. Thus, the unsaturatedpolyalkylene glycol type copolymer which satisfies such necessaryconditions as these exhibits a high dispersing ability and a highlyexcellent anti-gelling property in addition to manifesting the samechelating ability as the conventional unsaturated polyalkylene glycoltype copolymer having an about equal weight average molecular weight.

The unsaturated polyalkylene glycol type copolymer according to thisinvention is preferred to have such a sulfur-containing group as asulfonic group linked to the terminal or the main chain thereof andpossess a high anti-gelling property as described above. By such asulfur-containing group as a sulfonic group linked to the terminal, itis made possible to exalt the dispersing ability and the chelatingability. Further, the copolymer is enabled to manifest a highanti-gelling property. Thus, this unsaturated polyalkylene glycol typecopolymer can be suitably utilized for a dispersant for inorganicpigments, a descaling agent, and a detergent builder.

The necessary condition that the copolymer be a polymer formed bypolymerizing the aforementioned monomer containing 30–99 mass % of(meth)acrylic acid type monomer and 1–70 mass % of an unsaturatedpolyalkylene glycol type monomer and optionally 0–60 mass % of awater-soluble monoethylenically unsaturated monomer in an aqueoussolution and have such a sulfur-containing group as a sulfonic grouplinked to the terminal or the side chain thereof will be described belowin conjunction with the method for the production of an unsaturatedpolyalkylene glycol type copolymer of this invention.

The fourth aspect of this invention is directed toward a method for theproduction of an unsaturated polyalkylene glycol type copolymer by thecopolymerization of a (meth)acrylic acid type monomer A and anunsaturated polyalkylene glycol type monomer B, wherein the combinationof one or more species respectively of a persulfate and a bisulfite isused as an initiator.

By having not only a persulfate but also a bisulfite incorporated as aninitiator in the aforementioned ranges, the produced unsaturatedpolyalkylene glycol type copolymer is prevented from acquiring anunnecessarily high molecular weight but enabled to acquire a lowmolecular weight efficiently. Moreover, the produced unsaturatedpolyalkylene glycol type copolymer has been enabled to have such asulfur-containing group as a sulfonic group introduced thereinquantitatively, specifically in such a quantity as fulfills the value Srepresenting the quantity of the sulfur element introduced specifiedabove. The fact that such a sulfur-containing group as a sulfonic groupcan be introduced quantitatively indicates that the persulfate and thebisulfite are functioning very satisfactorily as an initiator. Thus, thereaction system of polymerization does not require addition of an excessinitiator and allows a further decrease in the quantity of the initiatorto be added. As a result, it is made possible to repress the rise of thecost of production of the polymer and enhance the efficiency ofproduction. The produced unsaturated polyalkylene glycol type copolymer,therefore, is capable of repressing the aggregation with a metal salt ofcalcium, for example, and acquiring a satisfactory anti-gellingproperty. Further, by controlling the quantity of the initiator to beadded to the reaction system of polymerization and the polymerizationtemperature within certain ranges, it is made possible to repress theemission of sulfur dioxide in a large quantity and allay the generationof an impurity as well. Thus, the further enhancement of the quality canbe realized, the rise of the cost of production of the polymer can berepressed, and the efficiency of production can be exalted.

The monomer to be used in the method of production of this invention isnot particularly restricted but is only required to be formed of amonomer component which is capable of producing the unsaturatedpolyalkylene glycol type copolymer by polymerization. Although it has tocontain at least a (meth)acrylic acid type monomer (hereinafteroccasionally referred to as “monomer A”) and an unsaturated polyalkyleneglycol type monomer (hereinafter occasionally referred to as “monomerB”), it may optionally contain additionally a monoethylenicallyunsaturated monomer copolymerizable with the monomers A and B(hereinafter occasionally referred to as “monomer C”). The term“monomer” as used herein refers to a monomer formed of monomercomponents and excludes a solvent, an initiator, and other additiveswhich are other components used in the polymerization.

As concrete examples of the monomer A component mentioned above, acrylicacid; methacrylic acid; salts formed by partially or completelyneutralizing (meth)acrylic acid with such an alkali metal as sodium orpotassium; and salts formed by partially or completely neutralizing theacid with either ammonia or an organic amine such as monoethanol amineor triethanol amine may be cited. These monomers may be used eithersingly or in the form of a combination of two or more members.Preferably, acrylic acid alone or a mixture formed by mixing acrylicacid and methacrylic acid at a prescribed ratio is used.

The quantity of the monomer A to be incorporated in the aforementionedmonomer is in the range of 30–99 mass %, preferably in the range of40–99 mass %, and more preferably in the range of 50–99 mass %, based onthe total mass of the monomer. If the quantity of the monomer A to beincorporated falls short of 30 mass %, the shortage will result inpreventing the chelating ability and the dispersing ability from beingmanifested in satisfactory balance.

The monomer A may be dissolved in a solvent which will be specificallydescribed herein below, preferably in water and incorporated in the formof a monomer A solution (preferably aqueous solution). The concentrationof the monomer A which is used as the monomer A solution (preferablyaqueous solution) is in the range of 10–100 mass %, preferably in therange of 30–95 mass %, and more preferably in the range of 50–90 mass %.If the concentration of the monomer A solution falls short of 10 mass %,the shortage will result in lowering the concentration of the productand complicating transportation and storage. Conversely, the upper limitof this quantity ought not be particularly restricted. It may be 100mass % (namely, solely) of monomer A (solution), i.e. total absence of asolvent.

As concrete examples of the monomer B component, compounds formed byadding 1–300 mol, preferably 1–100 mol, and more preferably 5–50 mol ofan alkylene oxide having 2–18 carbon atoms to 1 mol of such anunsaturated alcohol as 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol,2-methyl-3-buten-2-ol, or an allyl alcohol may be cited. As concreteexamples of alkylene oxides having 2–18 carbon atoms, styrene oxide,ethylene oxide, and propylene oxide may be cited. Among other alkyleneoxides enumerated above, ethylene oxide and/or propylene oxide is usedpreferably. When ethylene oxide and propylene oxide are used incombination, the order of linkage thereof is not restricted.

If the number of mols of ethylene oxide and/or propylene oxide to beadded is 0, the effect of this invention cannot be manifested fully. Ifthis number exceeds 300, the excess will result in preventing the effectof this invention from being enhanced and simply necessitating a largeincrease in the quantity for addition.

The quantity of the monomer B to be incorporated in the aforementionedmonomer is in the range of 1–70 mass %, preferably 1–50 mass %, and morepreferably in the range of 1–30 mol %, based on the total mass of themonomer. If the quantity of the monomer B to be incorporated falls shortof 1 mass %, the shortage will result in preventing the chelatingability and the dispersing ability from being manifested in a harmoniousbalance.

The monomer B may be dissolved in the solvent which will be specificallydescribed herein below, preferably in water and incorporated in the formof a monomer B solution (preferably aqueous solution). The concentrationof the monomer B when used in the form of the monomer B solution(preferably aqueous solution) is in the range of 10–100 mass %,preferably in the range of 30–95 mass %, and more preferably in therange of 50–90 mass %. If the concentration of the monomer B solutionfalls short of 10 mass %, the shortage will result in lowering theconcentration of the product and complicating transportation and storageo the product. The upper limit of this quantity ought not beparticularly restricted. It may be 100 mass % (namely, solely) ofmonomer B (solution), i.e. total absence of a solvent.

The novel water-soluble copolymer according to this invention isobtained by copolymerizing a monomer component essentially containing a(meth)acrylic acid type monomer A and an unsaturated polyalkylene glycoltype monomer B. The monomer component mentioned above may optionallycontain besides the monomers A and B a monoethylenically unsaturatedmonomer C which is copolymerizable with the monomers A and B.

The monoethylenically unsaturated monomer C mentioned above is notparticularly restricted. As concrete examples of this monomer C,styrene; styrene sulfonic acid; vinyl acetate; (meth)acrylonitrile;(meth)acrylamide; methyl (meth)acrylate; ethyl (meth)acrylate; butyl(meth)-acrylate; 2-ethylhexyl (meth)acrylate; dimethyl aminoethyl(meth)acrylate; diethyl aminoethyl (meth)acrylate; allyl alcohol;3-methyl-3-buten-1-ol; 3-methyl-2-buten-1-ol; 2-methyl-3-buten-1-ol;3-(meth)acryloxy-1,2-dihydroxy propane;3-(meth)acryloxy-1,2-di(poly)-oxyethylene ether propane;3-(meth)acryloxy-1,2-di(poly)oxypropylene ether propane;3-(meth)acryloxy-1,2-dihydroxypropane phosphate and monovalent metalsalts, divalent metal salts, ammonium salts, organic amine salts, ormono or diesters thereof with an alkyl group of 1–4 carbon atoms;3-(meth)acryloxy-1,2-dihydroxypropane sulfate and monovalent metalsalts, divalent metal salts, ammonium salts, organic amine salts, andesters thereof with an alkyl group of 1–4 carbon atoms;3-(meth)acryloxy-2-hydroxypropane sulfonic acid and monovalent metalsalts, divalent metal salts, ammonium salts, organic amine salts, andesters thereof with an alkyl group of 1–4 carbon atoms;3-(meth)acryloxy-2-(poly)oxyethylene ether propane sulfonic acid andmonovalent metal salts, divalent metal salts, ammonium salts, organicamine salts, and esters thereof with an alkyl group of 1–4 carbon atoms;monovalent metal salts, divalent metal salts, ammonium salts, organicamine salts, and esters thereof with an alkyl group of 1–4 carbon atoms;3-(meth)acryloxy-2-(poly)oxypropylene ether propane sulfonic acid andmonovalent metal salts, divalent metal salts, ammonium salts, organicamine salts, and esters thereof with an alkyl group of 1–4 carbon atoms;3-allyloxypropane-1,2-diol; 3-allyloxy-propane-1,2-diol phosphate;3-allyloxypropane-1,2-diol sulfonate; 3-allyloxypropane-1,2-diolsulfate; 3-allyloxy-1,2-di(poly)oxyethylene ether propane;3-allyloxy-1,2-di(poly)oxyethylene ether propane phosphate;3-allyoxy-1,2-di(poly)oxyethylene ether propane;3-allyloxy-1,2-di(poly)oxyethylene ether propane phosphate;3-allyloxy-1,2-di(poly)oxyethylene ether propane sulfonate;3-allyloxy-1,2-di(poly)oxypropylene ether propane;3-allyloxy-1,2-di(poly)oxypropylene ether propane phosphate;3-allyoxy-2,2-di(poly)oxypropylene ether propane sulfonate;6-allyloxy-hexan-1,2,3,4,5-pentaol;6-allyloxy-hexan-1,2,3,4,5-pentaolphosphate;6-allyloxy-hexan-1,2,3,4,5-pentaol sulfonate;6-allyloxy-hexan-1,2,3,4,5-penta(poly)oxyethylene ether hexane;6-allyoxy-hexan-1,2,3,4,5-penta-(poly)oxypropylene ether hexane; vinylsulfonic acid, allyl sulfonic acid, 3-allyloxy-2-hydroxy-propanesulfonic acid, 3-allyloxy-2-(poly)-oxyethylene propane sulfonic acid,3-allyloxy-2-(poly)oxypropylene propane sulfonic acid andmonoethylenically unsaturated monomers having a sulfonic group andmonovalent metal salts, divalent metal salts, ammonium salts, andorganic amine salts thereof o phosphoric esters or sulfate esters ofsuch compounds and monovalent metal salts, divalent metal salts,ammonium salts, and organic amine salts thereof; monoethylenicallyunsaturated aliphatic monocarboxylic acids such as (meth)acrylic acid,crotonic acid, and α-hydroxyacrylic acid; salts formed by partially orcompletely neutralizing the monoethylenically unsaturated aliphaticmonocarboxylic acids with an alkali metal; salts formed by partially orcompletely neutralizing the monoethylenically unsaturated aliphaticmonocarboxylic acids with either ammonia or such an organic amine asmonoethanol amine or triethanol amine; monoethylenically unsaturatedaliphatic dicarboxylic acids such as maleic acid, fumaric acid, anditaconic acid; salts formed by partially or completely neutralizing themonoethylenically unsaturated aliphatic dicarboxylic acids with analkali metal; and salts formed by partially or completely neutralizingthe monoethylenically unsaturated aliphatic dicarboxylic acid witheither ammonia or such an organic amine as monoethanol amine ortriethanol amine may be cited, though not exclusively.

The method of this invention prefers the monomer to be polymerized in anaqueous solution. This aqueous solution contains a solvent, aninitiator, and other additives.

The solvent to be used in the reaction system of polymerization when themonomer is polymerized in the aqueous solution is preferred to be suchan aqueous solvent as water, alcohol, glycol, glycerin, or apolyethylene glycol. Water is particularly preferable. These solventsmay be used either singly or in the form of a combination of two or moremembers. For the purpose of improving the solubility of the monomer inthe solvent, an organic solvent may be properly added in such aproportion as avoids exerting an adverse effect on the polymerization ofeach of the monomers.

As concrete examples of the organic solvent mentioned above, loweralcohols such as methanol and ethanol; amides such as dimethylformaldehyde; and ethers such as diethyl ether and dioxane may be cited.These organic solvents may be used either singly or in the form of acombination of two or more members.

The quantity of the solvent mentioned above to be used is in the rangeof 40–200 mass %, preferably in the range of 45–180 mass %, and morepreferably in the range of 50–150 mass %, based on the total mass of themonomer. If the quantity of this monomer to be used falls short of 10mass %, the shortage will result in heightening the molecular weight.Conversely, if the quantity of the solvent to be used exceeds 200 mass%, the excess will result in lowering the concentration of the producedunsaturated polyalkylene glycol type copolymer and possiblynecessitating removal of the solvent. The greater part or the whole ofthe solvent may be placed in the reaction vessel during the initialstage of the polymerization. Part of the solvent may be properly added(dropwise) independently into the reaction vessel during the process ofpolymerization. Otherwise, the monomer component, the initiatorcomponent, and other additives may be dissolved in advance in thesolvent and these components may be properly added (dropwise) togetherinto the reaction vessel during the process of the polymerization.

The initiator to be used in the reaction system for polymerization whenthe monomer is polymerized in the aqueous solution is preferred to be inthe form of the combination of one or more species respectively of apersulfate and a bisulfite. By using the initiator in this manner, it ismade possible to obtain a water-soluble polymer of a low molecularweight excelling not only in anti-gelling property but also indispersing ability and chelating ability and enable the operation andthe effect of this invention to be manifested effectively. By adding thebisulfite besides the persulfate to the initiator system, it is madepossible to repress impartation of an unnecessarily high molecularweight to the produced polymer and permit efficient production of thepolymer of a low molecular weight.

As concrete examples of the persulfate mentioned above, sodiumpersulfate, potassium persulfate, and ammonium persulfate may be cited.As concrete examples of the bisulfite, sodium bisulfite, potassiumbisulfite and ammonium bisulfite may be cited. It is permissible to usea sulfite or a hyposulfite in the place of the bisulfite.

The ratio of the quantity of the persulfate and the quantity of thebisulfite to be added is such that the proportion of the bisulfite is inthe range of 0.1–10 parts by mass, preferably in the range of 0.5–5parts by mass, and more preferably in the range of 1–3 parts by massrelative to 1 part by weight of the persulfate. If the proportion of thebisulfite falls short of 0.1 part by mass relative to 1 part by mass ofthe persulfate, the shortage will result in preventing the bisulfitefrom producing a sufficient effect, possibly disabling the introductionof a sulfonic group to the terminal of the polymer in such a quantity assatisfies the value S representing the quantity of the sulfur elementintroduced defined above, and disposing the unsaturated polyalkyleneglycol type copolymer to increase the weight average molecular weight.Conversely, if the proportion of the bisulfite exceeds 10 parts by massrelative 1 part by mass of the persulfate, the excess will result ininducing excess supply of the bisulfite to the reaction system ofpolymerization while the effect of the bisulfite has not beenproportionated to the ratio of addition, consequently suffering theexcess bisulfite to undergo decomposition in the reaction system andemit sulfur dioxide in a large quantity, and further inducing occurrenceof an impurity in the unsaturated polyalkylene glycol type copolymer,entailing degradation of the performance of the produced unsaturatedpolyalkylene glycol type copolymer and precipitation of an impurityduring the preservation at a low temperature.

The quantity of the aforementioned initiator comprising a persulfate anda bisulfite to be added is such that the total quantity of thepersulfate and the bisulfite of the initiator is in the range of 1–30 g,preferably in the range of 3–20 g, and more preferably 5–15 g based on 1mol of the monomer. Even when the persulfate and the bisulfite are addedin such a small total quantity as this, this invention is enabled torepress remarkably the emission of sulfur dioxide and the generation ofan impurity during the process of production because it causes itmanages to repress the polymerization temperature to a low level. Thus,the produced unsaturated polyalkylene glycol type copolymer is enabledto have such a sulfur-containing group as a sulfonic group introduced tothe terminal or the side chain thereof in such a quantity as satisfiesthe value S representing the quantity of the sulfur element introduceddefined above. Besides, the produced unsaturated polyalkylene glycoltype copolymer can be prevented from the degradation of performance andthe precipitation of an impurity during the preservation at a lowtemperature. If the total quantity of the persulfate and the bisulfiteof the aforementioned initiator falls short of 1 g, the shortage willresult in inevitably heightening the molecular weight of the producedpolymer, possibly disabling the introduction of such a sulfur-containinggroup as a sulfonic group to the terminal of the produced unsaturatedpolyalkylene glycol type copolymer in such a quantity as satisfies thevalue S representing the quantity of the sulfur element introduceddefined above, and disposing the polymer to increase the weight averagemolecular weight. Conversely, if the quantity of addition exceeds 30 g,the excess will result in preventing the persulfate and the bisulfite ofthe initiator from producing an effect proportionately to the quantityof addition and inducing such adverse effects as lowering the purity ofthe produced unsaturated polyalkylene glycol type copolymer.

The aforementioned persulfate which is one of the components of theinitiator may be dissolved in the aforementioned solvent, preferably inwater and incorporated in the form of a sulfate solution (preferablyaqueous solution) The concentration of the persulfate when thepersulfate is used in the form of a persulfate solution (preferablyaqueous solution) is in the range of 1–35 mass %, preferably in therange of 5–35 mass %, and more preferably in the range of 10–30 mass %.If theconcentrationof the sulfate solution falls short of 1 mass %, theshortage will result in lowering the concentration of the product andcomplicating transportation and preservation. Conversely, if theconcentration of the persulfate solution exceeds 35 mass %, the excesswill result in possibly inducing precipitation of the persulfate.

The bisulfite which is one of the components of the initiator may bedissolved in the aforementioned solvent, preferably in water andincorporated in the form of a bisulfite solution (preferably an aqueoussolution). The concentration of the bisulfite when the bisulfite is usedin the form of a bisulfite solution (preferably an aqueous solution) isin the range of 10–40 mass %, preferably in the range of 20–40 mass %,and more preferably in the range of 30–40 mass %. If the concentrationof the bisulfite solution falls short of 10 mass %, the shortage willresult in inevitably lowering the concentration of the product andcomplicating transportation and preservation. Conversely, if theconcentration of the bisulfite solution exceeds 40 mass %, the excesswill result in possibly inducing precipitation of the bisulfite.

This invention does not exclude such a mode of embodiment as uses theinitiator mentioned above in conjunction with other initiator (inclusiveof a chain transfer agent). When necessary, such other initiator as thismay be properly used in a quantity incapable of exerting an adverseeffect on the operation and the effect of this invention. Further inthis invention, the aforementioned combination of a persulfate and abisulfite is suitably used as initiator. The initiator, however, doesnot need to be particularly limited to this combination. The initiatorwhich is capable of introducing such a sulfur-containing group as asulfonic group in such as satisfies the value S defined above andallowing the polymer of a low molecular weight to be produced byone-step polymerization can be effectively used in this invention.

The other initiator mentioned above and the manner of addition thereofare the same as are already described concerning the method for theproduction of a (meth)acrylic acid type polymer and, therefore, will beomitted from the following description.

In the polymerization of the aforementioned monomer, the polymerizationtemperature is generally in the range of 25–99° C. The polymerizationtemperature is preferably not lower than 50° C. and more preferably notlower than 70° C. The polymerization temperature is preferably nothigher than 95° C. and more preferably not higher than 90° C. Thepolymerization maybe performed at a temperature of lower than 90. Therange of this temperature is preferably 50–95° C. and more preferably70–90° C. If the polymerization temperature falls short of 25° C., theshortage will result in raising the molecular weight, increasing theimpurity, and elongating the polymerization time so much as to degradethe productivity. Conversely, if the polymerization temperature exceeds99° C., the excess will result in inducing decomposition of thebisulfite of the initiator and emission of sulfur dioxide in a largequantity, consequently suffering the sulfur dioxide to dissolve in theliquid phase and form an impurity after polymerization and escape fromthe system during the process of polymerization and necessitate a costlytreatment for recovery, preventing the added initiator from producing asatisfactory effect proportionately to the quantity of addition becauseof the escape of the bisulfite of the initiator in the form of sulfurdioxide, and disabling the reduction of the molecular weight. The term“polymerization temperature” as used herein refers to the temperature ofthe reaction solution in the reaction system.

The polymerization temperature does not need to be constantly retainedapproximately at a fixed level throughout the whole course ofpolymerization. The information about this polymerization temperature isthe same as already described concerning the method for the productionof a (meth)acrylic acid type polymer and, therefore, will be omittedfrom the following description.

In the polymerization of the aforementioned monomer, the pressure in thereaction system is not particularly restricted. The information aboutthis pressure is the same as already described concerning the method forthe production of a (meth)acrylic acid type polymer and, therefore, willbe omitted from the following description.

The information about the atmosphere in the reaction system is the sameas already described concerning the method for the production of a(meth)acrylic acid type polymer and, therefore, will be omitted from thefollowing description.

In the method of production of this invention, the polymerization of theaforementioned monomer is preferred to be performed under an acidcondition. The information about the acid condition is the same asalready described concerning the method for the production of a(meth)acrylic acid type polymer and, therefore, will be omitted from thefollowing description. The information about the preferred pH and the pHadjusting agent is the same as already described concerning the methodfor the production of a (meth)acrylic acid type polymer and, therefore,will be omitted from the following description.

The degree of neutralization in the process of polymerization is in therange of 1–25 mol %, preferably in the range of 2–15 mol %, and morepreferably in the range of 3–10 mol %. If the degree of neutralizationfalls short of 1 mol %, the shortage will result in increasing thequantity of sulfur dioxide to be emitted and possibly increasing themolecular weight. Conversely, if the degree of neutralization in theprocess of polymerization exceeds 25 mol %, the excess will result inpossibly degrading the efficiency of chain transfer of the bisulfite andincreasing the molecular weight, suffering the viscosity of the aqueoussolution in the reaction system of polymerization to increaseconspicuously in consequence of the advance of polymerization,consequently inducing an unnecessarily large increase in the molecularweight of the produced polymer and disabling the production of a polymerof a low molecular weight, and further preventing the effect of thedecrease of the degree of neutralization from being sufficientlymanifested and possibly rendering it difficult to decrease the impuritymarkedly.

The method for effecting the neutralization is not particularlyrestricted. The information about the method for effecting theneutralization is the same as already described regarding the method forthe production of a (meth)acrylic acid type polymer and, therefore, willbe omitted from the following description.

In preparation for the polymerization, the aforementioned monomer, thepersulfate and the bisulfite of the initiator system, and otheradditives are generally dissolved in advance in a proper solvent(preferably a solvent of the same kind as the solvent used for theliquid directed toward dropwise addition) to form respectively a monomersolution, a persulfate solution, a bisulfite solution, and an additivesolution. Then, these solutions are preferred to be continuously addeddropwise into the (aqueous) solvent (optionally adjusted to a prescribedtemperature) placed in the reaction vessel over a prescribed duration ofdropwise addition to effect the expected polymerization. Further, partof the aqueous solvent may be added dropwise later separately from thesolvent initially placed in advance in the container of the reactionsystem. The method of production of this invention, however, is notlimited to such a procedure as this. As regards the method of dropwiseaddition, for example, the dropwise addition may be performed eithercontinuously or intermittently as divided into several small fractions.The monomer may be placed partially or wholly by way of initial charging(namely, the whole or part of the monomer may be regarded as addeddropwise all at once at the time of starting the polymerization). Asregards the speed of the dropwise addition of the monomer (the quantityof the monomer added dropwise), the dropwise addition may be performedat a fixed speed (fixed quantity) constantly from the start till thecompletion of the dropwise addition. Otherwise, the speed of thedropwise addition (the quantity of the monomer added dropwise) may bevaried along the course of time, depending on such factors as thepolymerization temperature. Instead of using one and the same speed forall the components for dropwise addition, the time for starting thepolymerization and the time for terminating it may be staggered from oneto another of the components for dropwise addition or the duration ofdropwise addition may be shortened or elongated. Thus, the method ofproduction of this invention may be properly altered within a rangeincapable of impairing the operation and the effect of the invention.When the individual components are added dropwise each in the form of asolution, the solutions for the dropwise addition may be heated to thesame level as the polymerization temperature in the reaction system.Owing to this measure, the polymerization temperature which is electedto be retained at a fixed level produces only a small variation andpermits easy adjustment.

Further, the bisulfite is such that the molecular weight thereof duringthe initial stage of polymerization largely affects the final molecularweight thereof. For the purpose of lowering the initial molecularweight, it is commendable to add dropwise the bisulfite or a solutionthereof in a proportion in the range of 5–20 mass % within 60 minutes,preferably within 30 minutes, and more preferably within 10 minutesafter the start of polymerization. This addition is particularlyeffective when the polymerization is initiated at room temperature asdescribed specifically afterward.

For the polymerization, it is important to lower the polymerizationtemperature, repress the emission of sulfur dioxide, and prevent theformation of an impurity. Thus, the polymerization requires the totalduration of dropwise addition to be so long as to fall in the range of180–600 minutes, preferably in the range of 210–480 minutes, and morepreferably in the range of 240–420 minutes. In consideration of theaforementioned problems encountered during the course of production andthe exaltation of performance of the produced polymer, this elongationof the duration of polymerization may well be rated as a significantmeasure. If the total duration of dropwise addition falls short of 180minutes, the shortage will result in preventing the persulfate and thebisulfite added as he initiator system from efficiently producing theeffect thereof, thus causing the produced unsaturated polyalkyleneglycol type copolymer to incur difficulty in introducing such asulfur-containing group as a sulfonic group to the terminal or the sidechain thereof in such a quantity as satisfies the value S representingthe quantity of the sulfur element introduced, consequently disposingthe polymer to heighten the weight average molecular weight thereof,possibly inducing the occurrence of an excess initiator owing to thequick dropwise addition of the initiator into the reaction system, andtherefore suffering the excess initiator to decompose, emit sulfurdioxide, discharge it from the system, and form an impurity. Conversely,if the total duration of dropwise addition exceeds 600 minutes, in spiteof the satisfactory performance of the produced polymer owing to therepressed emission of sulfur dioxide, the excess will result indegrading the productivity of the unsaturated polyalkylene glycol typecopolymer and possibly imposing a limit on the uses to be found. Theterm “total duration of dropwise addition” as used herein refers to thelength of time which intervenes between the time of the dropwiseaddition of the first component for dropwise addition (not necessarilylimited to one component) is initiated and the time of the dropwiseaddition of the last component for dropwise addition (not necessarilylimited to one component) is completed.

As regards the duration of dropwise addition of the bisulfite or thesolution thereof among other components for dropwise addition during theprocess of polymerization, the termination of this dropwise addition isadvanced by an interval of 1–30 minutes, preferably 1–20 minutes, andmore preferably 1–15 minutes from the termination of the dropwiseaddition of the monomer or the solution thereof. The information aboutthis procedure is the same as already described concerning the(meth)acrylic acid type polymer and, therefore, will be omitted from thefollowing description.

As regards the duration of dropwise addition of the persulfate(solution) among other components for dropwise addition during theprocess of polymerization, the termination of this dropwise addition isadvanced by an interval of 1–30 minutes, preferably 1–20 minutes, andmore preferably 1–15 minutes from the termination of the dropwiseaddition of the monomer (solution). The information about this procedureis the same as already described concerning the (meth)acrylic acid typepolymer and, therefore, will be omitted from the following descriptionthe excess.

The solid component concentration in the aqueous solution (namely thesolid component concentration of the monomer) at the time that thedropwise addition of each of the components mentioned above isterminated and the reaction of polymerization in the reaction system ofpolymerization is terminated exceeds 35 mass % and preferably falls inthe range of 40–70 mass %, and more preferably in the range of 45–65mass %. The information about this solid component concentration is thesame as already described regarding the (meth)acrylic acid type polymerand, therefore, will be omitted from the following description.

In the method for the production of an unsaturated polyalkylene glycoltype copolymer of this invention, the polymerization is carried outunder the aforementioned acid condition (the pH of the reaction solutionin the process of polymerization falling in the range of 1–6 at 25° C.and the degree of neutralization in the process of polymerizationfalling in the range of 1–25 mol %). The information about the degree ofneutralization under the acid condition is the same as already describedwith the (meth)acrylic acid type polymer and, therefore, will be omittedfrom the following description.

The unsaturated polyalkylene glycol type copolymer of this invention maybe produced either batchwise or continuously.

The method for the production of an unsaturated polyalkylene glycol typecopolymer of this invention is characterized by using as an initiatorthe combination of one or more species respectively of a persulfate anda bisulfite, wherein the bisulfite is used in a proportion in the rangeof 0.1–10 by mass ratio relative to the mass of the persulfate taken as1, the total quantity of the persulfate and the bisulfite to be added tothe reaction system of polymerization is in the range of 1–30 g per molof the monomer, and the polymerization temperature is in the range of25–99° C. Here, the polymerization is preferred to be performed under anacid condition (the pH of the reaction solution in the process ofpolymerization falling in the range of 1–6 at 25° C. and the degree ofneutralization during the course of polymerization falling in the rangeof 1–25 mol %), with the durations of dropwise addition of theindividual components for dropwise addition adjusted in the meanwhile.Preferably, the solid component concentration at the time of terminationof the polymerization is not less than 35 mass % and the weight averagemolecular weight of the produced polymer is in the range of 2000–100000.When the weight average molecular weight of the produced unsaturatedalkylene glycol type copolymer is in the aforementioned range, thequantity of the initiator added to the reaction system of polymerizationcan be markedly repressed so as to favor the cost of production and theemission of sulfur dioxide and the occurrence of an impurity during theprocess of production can be effectively and efficiently prevented(repressed) as well. Thus, an unsaturated polyalkylene glycol typecopolymer capable of conspicuously and effectively manifesting variousproperties as high dispersibility, a high chelating ability, and a highanti-gelling property at high levels can be efficiently produced. Thatis, a polymer of high quality suitably applicable to a dispersant ofinorganic pigments, a descaling agent, and a detergent builder can beproduced at a low cost. Further, the cost can be decreased as byrepressing an increase in the quantity of the initiator to be added tothe reaction system of polymerization.

As concrete examples of the use found for the unsaturated polyalkyleneglycol type copolymer of this invention, aqueous dispersants (inclusiveof calcium carbonate, kaolin, and a pigment dispersant), water treatingagents, descaling agents (scale repressing agent), cement additives,detergent builders (inclusive of liquid and pulverulent detergents), anddetergents using the builders may be cited, though not exclusively. Thecopolymer ought not be limited to these uses but may be utilized in awide variety of applications. It can be applied to metal ion bindingagents, thickeners, and various types of binders, for example.

The aqueous dispersant of this invention is characterized by containingan unsaturated polyalkylene glycol type copolymer (inclusive of theproduct of purification of such an unsaturated polyalkylene glycol typecopolymer as mentioned above). Since the unsaturated polyalkylene glycoltype polymer has the impurity content thereof decreased markedly, it canprovide an aqueous dispersant of a low molecular weight which manifestsveritably excellent dispersibility, chelating ability, and anti-gellingproperty inherent in an unsaturated polyalkylene glycol type copolymer.It also provides an aqueous dispersant which enjoys very high qualityand performance and excels in stability such that it is incapable ofinducing either degradation of performance during the protractedpreservation or precipitation of an impurity during the preservation ata low temperature.

In the descaling agent of this invention, the components of compositionother than the unsaturated polyalkylene glycol type copolymer and theirproportions of incorporation are not particularly restricted. Thisdescaling agent can be suitably applied (utilized) in a quantityincapable of impairing the operation and the effect of this invention,based on the various components and their proportions of incorporationeffectively applied to the conventional aqueous dispersant.

The descaling agent of this invention is characterized by containing anunsaturated polyalkylene glycol type copolymer (inclusive of the productof purification of such an unsaturated polyalkylene glycol typecopolymer as mentioned above). Since the unsaturated polyalkylene glycoltype polymer has the impurity content thereof decreased markedly, it canprovide a water-soluble descaling agent of a low molecular weight whichmanifests veritably excellent dispersibility, chelating ability, andanti-gelling property inherent in an unsaturated polyalkylene glycoltype copolymer. It also provides a descaling agent which enjoys veryhigh quality and performance and excels in stability such that it isincapable of inducing either degradation of performance during theprotracted preservation or precipitation of an impurity during thepreservation at a low temperature.

The cement additive of this invention is characterized by containing anunsaturated polyalkylene glycol type copolymer (inclusive of the productof purification of such an unsaturated polyalkylene glycol typecopolymer as mentioned above). Since the unsaturated polyalkylene glycoltype polymer has the impurity content thereof decreased markedly, it canprovide a water-soluble cement additive of a low molecular weight whichmanifests veritably excellent dispersibility, chelating ability, andanti-gelling property inherent in an unsaturated polyalkylene glycoltype copolymer. It also provides a cement additive which enjoys veryhigh quality and performance and excels in stability such that it isincapable of inducing either degradation of performance during theprotracted preservation or precipitation of an impurity during thepreservation at a low temperature.

In the cement additive of this invention, the components of compositionother than the unsaturated polyalkylene glycol type copolymer and theirproportions of incorporation are not particularly restricted. Thiscement additive can be suitably applied (utilized) in a quantityincapable of impairing the operation and the effect of this invention,based on the various components and their proportions of incorporationeffectively applied to the conventional cement additive.

The detergent builder of this invention is characterized by containingan unsaturated polyalkylene glycol type copolymer (inclusive of theproduct of purification of such an unsaturated polyalkylene glycol typecopolymer as mentioned above). Since the unsaturated polyalkylene glycoltype polymer has the impurity content thereof decreased markedly, it canprovide a water-soluble detergent builder of a low molecular weightwhich manifests veritably excellent compatibility with a liquiddetergent, dispersibility, chelating ability, and anti-gelling propertyinherent in an unsaturated polyalkylene glycol type copolymer. Thedetergent builder, in actual use, exhibits an excellent ability toprevent soil redeposition. It also provides a detergent builder whichenjoys very high quality and performance and excels in stability suchthat it is incapable of inducing either degradation of performanceduring the protracted preservation or precipitation of an impurityduring the preservation at a low temperature.

In the detergent builder of this invention, the components ofcomposition other than the unsaturated polyalkylene glycol typecopolymer and their proportions of incorporation are not particularlyrestricted. This detergent builder can be suitably applied (utilized) ina quantity incapable of impairing the operation and the effect of thisinvention, based on the various components and their proportions ofincorporation effectively applied to the conventional detergent builder.

The detergent of this invention is characterized by containing anunsaturated polyalkylene glycol type copolymer (inclusive of the productof purification of such an unsaturated polyalkylene glycol typecopolymer as mentioned above). Since the unsaturated polyalkylene glycoltype polymer has the impurity content thereof decreased markedly, it canprovide a water-soluble detergent of a low molecular weight whichmanifests veritably excellent dispersibility, chelating ability, andanti-gelling property inherent in an unsaturated polyalkylene glycoltype copolymer. It also provides a detergent which enjoys very highquality and performance and excels in stability such that it isincapable of inducing either degradation of performance during theprotracted preservation or precipitation of an impurity during thepreservation at a low temperature.

Preferably in the detergent of this invention, the quantity of anunsaturated polyalkylene glycol type copolymer to be incorporated is inthe range of 1–20 mass % based on the total mass of the detergent andthe quantity of a surfactant to be incorporated is in the range of 5–70mass % based on the total mass of the detergent. Optionally, thisdetergent may incorporate therein an enzyme in a quantity of not morethan 5 mass %.

If the quantity of an unsaturated polyalkylene glycol type copolymerincorporated in the detergent falls short of 1 mass %, the shortage willresult in preventing the effect of this addition from being manifested.Conversely, if this quantity exceeds 20 mass %, the excess will be at adisadvantage economically in preventing the effect of addition frombeing linked to the exaltation of deterging power. If the quantity ofthe surfactant which is the principal component of the detergentdeviates from the range mentioned above, this deviation will result inpossibly upsetting the balance of the surfactant with other componentsand exerting an adverse effect on the deterging power of the detergent.When an enzyme is incorporated in the detergent, it will contribute tothe exaltation of deterging power. If the quantity of the enzyme to beincorporated exceeds 5 mass %, however, the excess will result inpreventing the effect of addition from being manifested and imperilingthe economy of the use of the enzyme.

The detergent builder according to this invention may be intended foruse in a liquid detergent or a pulverulent detergent. Since theunsaturated polyalkylene glycol type copolymer excels in compatibilitywith a surfactant which will be specifically described herein below, itpermits production of a liquid detergent of a high concentration. In thelight of this fact, it is commendable to use the unsaturatedpolyalkylene glycol type copolymer of this invention as a builder for aliquid detergent.

The information about the surfactant and the enzyme which can be usedherein is the same as already described concerning the (meth)acrylicacid type polymer and, therefore, will be omitted from the followingdescription.

Further, the detergent of this invention may optionally incorporatetherein a known alkali builder. The information about the incorporationof an alkali builder is the same as already described regarding the(meth)acrylic acid type polymer and, therefore, will be omitted from thefollowing description.

The manner of incorporating an unsaturated polyalkylene glycol typecopolymer in the detergent of this invention is decided in accordancewith the form in which the detergent is marketed (a liquid product or asolid product, for example) and ought not be particularly restricted.The copolymer may be incorporated in the form of an aqueous solutionassumed at the end of polymerization. Otherwise, it may be incorporatedin a state concentrated by expelling the water content thereof to acertain degree. Alternatively, it may be incorporated in a statesolidified to dryness.

This detergent embraces detergents such as bleaching detergents havingone function of the component thereof enriched which are usedexclusively for specific purposes besides synthetic detergents forhousehold use, industrial detergents directed toward textile industryand other industries, and hard facial detergents.

EXAMPLES

Now, this invention will be described more specifically below withreference to working examples and comparative examples. This inventionis not restricted in any respect by these examples. The symbol “%”entered in the working examples and the comparative examples represents“mass %” unless otherwise specified.

<Regarding (meth)acrylic Acid Type Polymer>

As regards the (meth)acrylic acid type polymer of this invention, (1-1)the quantity of S contained in the polymer and the total quantity of Sand the method for dialysis to be used in the determination thereof,(1-2) the weight average molecular weight (Mw) and the number averagemolecular weight (Mn) of the polymer, (1-3) the degree of gelation, q,to be used in determining the value Q representing the anti-gellingability, (1-4) the NMR to be used in determining the value R, (1-5) theiron ion concentration, (1-6) the Ca-binding capacity, (1-7) thequantity of sulfur dioxide emitted, (1-8) the quantity of precipitationat a low temperature, and (1-9) the method for determining the sulfurdioxide component are shown below.

(1-1) Determination of the Quantity of S Contained in the Polymer andthe Total Quantity of S.

The quantity of S in the (meth)acrylic acid type polymer obtained bypolymerization before and after the treatment of dialysis was determinedby the inductively coupled plasma (ICP) emission spectroscopy. Here, thequantity of S of the (meth)acrylic acid type polymer prior to thetreatment of dialysis was designated “the total quantity of S.” Thequantity of S of the (meth)acrylic acid type polymer after the treatmentof dialysis was designated as “the quantity of S contained in thepolymer.” The method of dialysis used herein will be described below.

<<Method of Dialysis>>

{circle around (1)} An aqueous solution of (meth)acrylic acid typepolymer having a solid component concentration of 30 mass % was preparedby adding a suitable quantity of water to a (meth)acrylic acid typepolymer obtained by polymerization. In a dialysis membrane 40 cm long,20 g of the aqueous solution was placed and sealed tightly. As thedialysis membrane was a Spectra/Por Membrane MWCO: 1000 having afractional molecular weight of 1000 (made by Spectrum LaboratoriesInc.). This invention allows use of a dialysis membrane having an aboutequal fractional molecular weight to the membrane just mentioned.

{circle around (2)} The dialysis membrane was immersed in 2000 g ofwater held in a 2-liter beaker and the water was agitated with astirrer.

{circle around (3)} After the agitation was continued for 6 hours, thedialysis membrane was withdrawn from the beaker and the content of thedialysis membrane was extracted after the outside of the dialysismembrane had been thoroughly rinsed with water.

{circle around (4)} The extract was concentrated with the use of anevaporator and the resultant concentrate was used as a sample of the(meth)acrylic acid type polymer after the treatment of dialysis.

As a sample of the (meth)acrylic acid type polymer prior to thetreatment of dialysis, the concentrate obtained by subjecting a(meth)acrylic acid type polymer obtained by polymerization as describedin the step {circle around (1)} mentioned above to the same treatmentwith an evaporator as described in the step {circle around (4)} wasused.

(1-2) Determination of Weight Average Molecular Weight (Mw) and NumberAverage Molecular Weight (Mw).

The weight average molecular weight (Mw) and the number averagemolecular weight (Mn) of a (meth)acrylic acid type polymer were bothdetermined by gel permeation chromatography (GPC). As the sample forthis determination, a (meth)acrylic acid type polymer obtained bypolymerization as described in the step {circle around (1)} of theparagraph (1) Method of dialysis was used in its unmodified form. Theconditions and the devices used for the determination were as follows.

A column made by Tosoh K.K. and sold under the trademark designation ofG-3000PWXL was used for the GPC.

As the mobile phase for the GPC, an aqueous solution prepared bydiluting 34.5 g of hydrogen disodium phosphate dodecahydrate and 46.2 gof dihydrogen sodium phosphate (both reagent chemicals) with purifiedwater to give a total weight of 5000 g and filtering the resultantaqueous solution through a 0.45 μm membrane filter was used.

As the detector, a sensor made by Waters Corp. and sold under theproduct code of “Model 481 type” and operated with a detectionwavelength of UV: 214 nm was used.

As the pump, a product of Hitachi, Ltd. sold under the trademarkdesignation of L-7110 was used.

The flow rate of the mobile phase was fixed at 0.5 ml/minute and thetemperature at 35° C. The calibration curve was prepared by using astandard sample of sodium polyacrylate made by Sowa Kagaku K.K.

(1-3) Determination of Degree of Gelation, q, and Value Q RepresentingAnti-Gelling Ability

For the determination of the degree of gelation, a borate buffersolution, an aqueous calcium chloride solution, and an aqueous 1%polymer solution were prepared. The borate buffer solution was formed bydiluting 7.42 g of boric acid, 1.75 g of sodium chloride, and 7.63 g ofsodium borate decahydrate with purified water to give a total weight of1000 g. The aqueous calcium chloride solution was formed by diluting0.735 g of calcium chloride dihydrate with purified water to give atotal weight of 2500 g. The aqueous 1% polymer solution mentioned abovewas formed by diluting a (meth)acrylic acid type polymer obtained bypolymerization as described in the step {circle around (1)} of theparagraph (1) Method of dialysis with a suitable water to give a solidcomponent concentration of 1 mass %.

Then, a tall beaker having an inner volume of 500 ml was charged withthe aforementioned solutions added in a prescribed order in prescribedquantities. The prescribed order and the prescribed quantities were asfollows: The beaker was charged firstly with 250 ml of purified water,secondly with 10 ml of the borate buffer solution, thirdly with 5 ml ofthe aqueous 1% polymer solution, and lastly with 250 ml of the aqueouscalcium chloride solution.

By mixing the solutions introduced in this order into the beaker, thepolymer contained in the aqueous 1% polymer solution was allowed to begelled and the resultant mixed solution was used as a test solution. Thetall beaker holding the test solution was stoppered and then leftstanding at rest for one hour in a constant temperature bath adjusted inadvance to 90° C. After the elapse of this one hour, the test solutionwas immediately transferred into a quartz cell 5 cm in depth andmeasured for absorbency, a, at an UV wavelength of 380 nm.

Separately, a blank solution was prepared by following the procedureused in the preparation of the test solution with the four componentsidentified above while using 250 ml of purified water in place of 250 mlof the aqueous calcium chloride solution, i.e. one of the fourcomponents mentioned above. This blank solution was processed in thesame manner as the test solution mentioned above and measured forabsorbency (blank value), b, at an UV wavelength of 380 nm. The degreeof gelation, q, was calculated by the formula, a-b, wherein a denotesthe absorbency and b the blank value.

The value Q representing the anti-gelling ability was calculated inaccordance with the formula, Q=Degree of gelation×10⁵/Mw, using thisdegree of gelation and the weight average molecular weight (Mw) obtainedby the determination described in (2) above.

(1-4) ¹H-NMR to be Used in Determining the Value R

-   Device: A product of Varian Corp. and sold under the trademark    designation of “Gemini 2000 (200 MHz)-   Solvent: D₂O-   Resonance frequency: 199.93 MHz-   Probe: A 5-mm switchable probe-   Nucleus for observation: Hydrogen nucleus-   Conditions for determination: Pulses of 90 degrees, 10 μsec.    (irradiation with 45-degree pulses)

Waiting time 1.254 sec Number of integrations 16 Temperature Roomtemperature

-   Method for preparation of sample: A sample was formed by diluting    0.1 g of a (meth)acrylic acid type polymer having the solvent    component thoroughly removed by vacuum drying with D₂O to give a    total weight of 1.0 g and completely dissolving the polymer.

(1-5) Determination of Iron Ion Concentration

A (meth)acrylic acid type polymer obtained by polymerization wasmeasured for iron ion concentration by the method of ICP emissionspectroscopy.

(1-6) Determination of Ca-Binding Capacity

In a beaker having an inner volume of 100 ml, 50 g of an aqueous 0.001mol/liter calcium chloride solution was placed. To the solution, 10 mgof poly(meth)acrylate as reduced to a solid content was added. Then,this aqueous solution was adjusted with diluted sodium hydroxidesolution to give a pH in the range of 9–11. Subsequently, the solutionwas kept stirred and 1 ml of an aqueous 4 mol/liter potassium chloridesolution was added to the stirred solution as a calcium ion electrodestabilizer.

The resultant solution was measured for free calcium ion with the use ofan ion analyzer (made by Orion K.K. and sold under the product code of“EA920 model”) and a calcium ion electrode (made by Orion K.K. and soldunder the product code of “93-20 model”) to find by calculation thequantity of calcium ion, mg reduced to calcium carbonate, which hadundergone chelation (the Ca-binding capacity, one form of chelatingability) per g of poly(meth)acrylate. The unit of the Ca-bindingcapacity which is one form of the chelating ability was “mg CaCO₃/g.”

(1-7) Quantity of Sulfur Dioxide Emitted (Quantity of Gas)

The quantity of the gas discharged between the time of startingpolymerization and the time of terminating polymerization was measuredby the use of a gas meter (made by Shinagawa K.K. and sold under thetrademark designation of “Dry Test Gas Meter Model DC-2”) connected to areflux condenser.

(1-8) Quantity of Precipitate at Low Temperature

{circle around (1)} In a 50-ml screw cap bottle measuring 32 mm ininside diameter, 50 g of a given aqueous polymer solution (the polymerof a working example or the polymer of a comparative example) was cooledto 0° C.

{circle around (2)} A small amount of single crystals of Na₂SO₄ wasplaced as seed crystals in the solution and left standing at rest at 0°C. for 12 hours.

{circle around (3)} Standard for evaluation: A precipitation of crystalsto not less than half of the height of the liquid level was rated as“many” and a precipitation of crystals less than this amount was ratedas “small.”

(1-9) Method for Quantitative Determination of Sulfur Dioxide Content

A solution (hereinafter referred to as “solution {circle around (2)}”)was prepared by mixing 20 g of an aqueous polymer solution (the polymerof a working example or the polymer of a comparative example) and 1 g ofan aqueous about 1% hydrogen peroxide solution (hereinafter referred toas “solution {circle around (1)}”) and stirring them together for 5minutes. Then, the solution {circle around (2)} was tested for thehydrogen peroxide concentration as follows.

In a Meyer flask having an inner volume of 300 ml, 2 g of potassiumiodide was placed and stirred together with 100 g of purified wateradded thereto with the use of a magnetic stirrer. When the potassiumiodide was completely dissolved, 30 ml of 18N (9 mol/(dm)³) sulfuricacid was added to the resultant aqueous solution. The produced solutionand about 18–20 g of the solution {circle around (2)} added thereto werestirred together in a state covered with a light shielding paper for 5minutes. The mixture consequently formed was titrated with a 0.1M sodiumthiosulfate. The titration was continued slowly till the solutionassumed a light yellow color. The solution and 1 ml of an aqueous 1%starch solution added thereto were together titrated till the color ofiodine starch disappeared (A ml). A blank (obtained by omitting theaddition of the solution {circle around (2)} in the procedure describedabove) was titrated in the same manner as described above (B ml). Thehydrogen peroxide concentration of the solution {circle around (2)} wascalculated in accordance with the following formula. The hydrogenperoxide concentration of the solution {circle around (1)} was similarlycalculated.

${{Hydrogen}\mspace{14mu}{peroxide}\mspace{14mu}{concentration}\mspace{14mu}(\%)} = \frac{( {A - B} ) \times 0.1M\mspace{14mu}{sodium}\mspace{14mu}{thiosulfate}\mspace{14mu}{factor} \times 17}{{Quantity}\mspace{14mu}{of}\mspace{14mu}{solution}\mspace{14mu}\mspace{14mu}{or}\mspace{14mu}{solution}\mspace{14mu}\mspace{14mu}(g)\mspace{14mu}{added}}$

Then, the hydrogen peroxide concentration (%) consumed in the solution{circle around (2)} was calculated.Hydrogen peroxide concentration (%) consumed in the solution {circlearound (2)}=[Hydrogen peroxide concentration (%) of solution {circlearound (1)}]×[(Solution {circle around (1)} (g)/Solution {circle around(2)} (g))−1]

The sulfur dioxide component present in the added solution {circlearound (2)} was calculated as reduced to sodium bisulfite in accordancewith the following formula.Sulfur dioxide component (g) present in added solution {circle around(2)}=(Hydrogen peroxide concentration (%) consumed in solution {circlearound (2)})/100×[Quantity of solution {circle around (2)} (g)added]×108/34

Finally, the sulfur dioxide content (g) in the whole aqueous polymersolution, namely all the aqueous polymer solution in the polymerizationkettle, was calculated as reduced to sodium bisulfite according to thefollowing formula.Sulfur dioxide content (g) in the whole aqueous polymersolution=(Bisulfurous acid content (g) present in added solution {circlearound (2)})×{Total quantity of aqueous polymer solution (g)}/[{Quantityof solution {circle around (2)} added (g)}×{(Quantity of aqueous polymersolution in solution {circle around (2)} (g))/(Solution {circle around(2)} (g)}]

Example 1

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 156.5 g of purifiedwater was placed (initial charging) and heated to 90° C. as kept in astirred state.

Then, to the reaction system of polymerization kept stirred at a fixedtemperature of about 90° C., 427.5 g (4.75 mols) of an aqueous 80%acrylic acid solution (hereinafter abbreviated as “80% AA”), 63.5 g(0.25 mol) of an aqueous 37% sodium acrylate solution (hereinafterabbreviated as “37% SA”), 66.7 g (2.0 g/mol as reduced relative to thequantity of monomer introduced (wherein, the term “the quantity ofmonomer introduced” as used herein means the total quantity of all themonomers introduced; which applies similarly hereinafter)) of an aqueous15% sodium persulfate solution (hereinafter abbreviated as “15% NaPS”),and 71.4 g (5.0 g/mol as reduced relative to the quantity of monomerintroduced) of an aqueous 35% sodium bisulfite solution (hereinafterabbreviated as “35% SBS”) were added dropwise through respectivelyindependent dropping nozzles. The duration of dropwise addition was 300minutes for the 80% AA, the 37% SA, and the 35% SBS each and 310 minutesfor the 15% NaPS. During each of the durations of dropwise addition, therelevant component was continuously dropped at a fixed speed ofdropping.

After termination of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to age the solution andterminate the polymerization. After completion of the polymerization,the reaction solution was left cooling and then neutralized by having366.7 g (4.40 mols) of an aqueous 48% sodium hydroxide solution(hereinafter abbreviated as “48% NaOH”) gradually added dropwise theretoas kept stirred. Thus, an aqueous solution containing sodiumpolyacrylate having a solid component concentration of 45 mass % and afinal degree of neutralization of 93 mol % (hereinafter referred to as“polymer (1)”) was obtained. The prescriptions for polymerizationinvolved herein are summarized in Table 1 below.

The polymer (1) consequently obtained was measured for molecular weight,value S, value R, value Q, iron ion concentration, Ca-binding capacity,quantity of gas, and quantity of precipitation at low temperature. Theresults are shown in Table 11.

Examples 2–14

Polymers of these examples were obtained by following the procedure ofexample 1. The prescriptions for these polymers were summarized in Table1 and Table 2 below.

The polymers (2)–(14) thus obtained were each measured for molecularweight, value S, value R, value Q, iron ion concentration, Ca-bindingcapacity, quantity of gas, and quantity of precipitation at lowtemperature. The results are shown in Table 11.

TABLE 1 Example 1 2 3 4 5 6 7 Polymer (1) (2) (3) (4) (5) (6) (7)Initial charge of (g) 156.5 140.0 145.0 160.0 165.0 135.0 165.0 purifiedwater Dropwise addition 80% AAaq (g) 427.5 405.0 405.0 405.0 405.0 405.0405.0 (mol) 4.75 4.50 4.50 4.50 4.50 4.50 4.50 37% SAaq (g) 63.5 127.0127.0 127.0 127.0 127.0 127.0 (mol) 0.25 0.50 0.50 0.50 0.50 0.50 0.5035% SBSaq (g) 71.4 114.3 85.7 114.3 85.7 114.3 71.4 (g/mol) 5.0 8.0 6.08.0 6.0 8.0 5.0 25% NaPSaq (g) 66.7 80.0 80.0 40.0 40.0 20.0 40.0(g/mol) 2.0 4.0 4.0 2.0 2.0 1.0 2.0 Purified water (g) 0.0 0.0 0.0 0.00.0 30.0 0.0 Duration of dropwise (min) addition 80% AAaq 0–300 0–2400–240 0–240 0–240 0–240 0–240 37% SAaq 0–300 0–240 0–240 0–240 0–2400–240 0–240 35% SBSaq 0–300 0–250 0–250 0–250 0–240 0–240 0–240 15%NaPSaq 0–310 0–250 0–250 0–250 0–250 0–250 0–250 Purified water — — — —— 0–250 — Polymerization (° C.) 90 90 90 90 90 90 90 temperature Agingtime (min) 30 30 30 30 30 30 30 Degree of (mol %) 5.0 10.0 10.0 10.010.0 10.0 10.0 neutralization after dropwise addition After treatment48% NaOHaq (g) 366.7 333.3 333.3 333.3 333.3 333.3 333.3 (mol) 4.40 4.004.00 4.00 4.00 4.00 4.00 Final degree of (mol %) 93.0 90.0 90.0 90.090.0 90.0 90.0 neutralization Polymerization SUS2.5L SUS2.5L SUS2.5LSUS2.5L SUS2.5L SUS2.5L SUS2.5L kettle Stirring vanes Paddle PaddlePaddle Paddle Paddle Paddle Paddle vanes vanes vanes vanes vanes vanesvanes

TABLE 2 Example 8 9 10 11 12 13 14 Polymer (8) (9) (10) (11) (12) (13)(14) Initial charge of (g) 165.0 137.8 137.8 98.0 156.5 158.5 156.5purified water Dropwise addition 80% AAaq (g) 405.0 405.0 405.0 405.0427.5 427.5 427.5 (mol) 4.50 4.50 4.50 4.50 4.75 4.75 4.75 37% SAaq (g)127.0 127.0 127.0 127.0 63.5 63.51 63.5 (mol) 0.50 0.50 0.50 0.50 0.250.25 0.25 35% SBSaq (g) 85.7 89.3 89.3 71.4 71.4 62.5 69.0 (g/mol) 6.06.3 6.3 5.0 5.0 4.4 4.8 15% NaPSaq (g) 66.7 66.7 66.7 133.3 66.7 66.766.7 (g/mol) 2.0 2.0 2.0 4.0 2.0 2.0 2.0 Duration of dropwise (min)addition 80% AAaq 0–240 10–250 10–250 0–240 0–240 0–240 0–240 37% SAaq0–240 10–250 10–250 0–240 0–240 0–240 0–240 35% SBSaq 0–240 0–250 0–2500–240 0–240 0–210 0–240 15% NaPSaq 0–250 10–260 10–260 0–250 0–250 0–2500–250 Polymerization (° C.) 70 70 90 90 90 90 90 temperature Aging time(min) 30 30 30 30 30 30 30 Degree of (mol %) 10.0 10.0 10.0 10.0 5.0 5.05.0 neutralization after dropwise addition After treatment 48% NaOHaq(g) 333.3 333.3 333.3 333.3 366.7 366.7 366.7 (mol) 4.00 4.00 4.00 4.004.40 4.40 4.40 Final degree of (mol %) 90.0 90.0 90.0 90.0 93.0 93.093.0 neutralization Polymerization SUS2.5L SUS2.5L SUS2.5L SUS2.5LSUS2.5L SUS2.5L SUS2.5L kettle Stirring vanes Paddle Paddle PaddlePaddle Paddle Paddle Paddle vanes vanes vanes vanes vanes vanes vanes

Examples 15–17

Polymers of these examples were obtained by following the procedure ofExample 1 while quickly adding 7.1 g (0.5 g/mol as reduced relative tothe quantity of polymer introduced) of 35% SBS immediately prior tostarting the dropwise addition of the 80% AA, 37% SA, 35% SBS, and 15%NaPS. The prescriptions for the polymers are summarized in Table 3below.

The polymers (15)–(17) obtained were each measured for molecular weight,value S, value R, value Q, iron ion concentration, Ca-binding capacity,quantity of gas, and quantity of precipitation at low temperature. Theresults are shown in Table 11 below.

TABLE 3 Example 15 16 17 Polymer (15) (16) (17) Initial charge of (g)137.0 137.0 137.0 purified water 35% SBSaq (g) 7.1 7.1 7.1 (g/mol) 0.50.5 0.5 Dropwise addition 80% AAaq (g) 405.0 405.0 405.0 (mol) 4.50 4.504.50 37% SAaq (g) 127.0 127.0 127.0 (mol) 0.50 0.50 0.50 35% SBSaq (g)85.7 85.7 85.7 (g/mol) 6.0 6.0 6.0 15% NaPSaq (g) 66.7 66.7 66.7 (g/mol)2.0 2.0 2.0 Duration of (min) dropwise addition 80% AAaq 0–240 0–2400–240 37% SAaq 0–240 0–240 0–240 35% SBSaq 0–240 0–240 0–240 15% NaPSaq0–250 0–250 0–250 Polymerization (° C.) 70 90 50 temperature Aging time(min) 30 30 30 Degree of (mol %) 10.0 10.0 10.0 neutralization afterdropwise addition After treatment 48% NaOHaq (g) 333.3 333.3 333.3 (mol)4.00 4.00 4.00 Final degree of (mol %) 90.0 90.0 90.0 neutralizationPolymerization SUS2.5L SUS2.5L SUS2.5L kettle Stirring vanes PaddlePaddle Paddle vanes vanes vanes

Example 18

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 137.0 g of purifiedwater was placed (initial charging) and heated to30° C. as kept in astirred state. Then, 7.1 g (0.5 g/mol as reduced relative to thequantity of monomer introduced) of 35% SBS was quickly added as stirredthereto. To the reaction system of polymerization thus obtained, 405.0 g(4.50 mols) of 80% AA, 127.0 g (0.50 mol) of 37% SA, 66.7 g (2.0 g/molas reduced relative to the quantity of monomer introduced) of 15% NaPS,and 85.7 g (6.0 g/mol as reduced relative to the quantity of monomerintroduced) of 35% SBS were added dropwise through respectivelyindependent dropping nozzles. The duration of dropwise addition was 240minutes for the 80% AA, the 37% SA, and the 35% SBS each and 250 minutesfor the 15% NaPS. The polymerization temperature wa selevated at a rateof 1° C. per minute after the polymerization was initiated at 30° C. andit was fixed at 90° C. after the elapse of 60 minutes following theinitiation of polymerization. During each of the durations of dropwiseaddition, the relevant component was continuously dropped at a fixedspeed of dropping.

After termination of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to age the solution andterminate the polymerization. After completion of the polymerization,the reaction solution was left cooling and then neutralized by having366.7 g (4.40 mols) of 48% NaOH gradually added dropwise thereto as keptstirred. Thus, an aqueous solution containing sodium polyacrylate havinga solid component concentration of 45 mass % and a final degree ofneutralization of 93 mol % (hereinafter referred to as “polymer (18)”)was obtained. The prescriptions for polymerization involved herein aresummarized in Table 4 below.

The polymer (18) consequently obtained was measured for molecularweight, value S, value R, value Q, iron ion concentration, Ca-bindingcapacity, quantity of gas, and quantity of precipitation at lowtemperature. The results are shown in Table 11.

Example 19

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 154.0 g of purifiedwater was placed (initial charging ) and heated to 30° C. as kept in astirred state. To the reaction system of polymerization thus obtainedand continuously kept stirred, 427.5 g (4.75 mols) of 80% AA, 63.5 g(0.25 mol) of 37% SA, 66.7 g (2.0 g/mol as reduced relative to thequantity of monomer introduced) of 15% NaPS, and 85.7 g (6.0 g/mol asreduced relative to the quantity of monomer introduced) of 35% SBS wereadded dropwise through respectively independent dropping nozzles. Theduration of dropwise addition was 300 minutes for the 80% AA, the 37%SA, and the 35% SBS each and 310 minutes for the 15% NaPS. In the caseof the 35% SBS, however, it was added dropwise to a total of 7.1 g (0.5g/mol as reduced relative to the quantity of monomer introduced) in 10minutes following the start of the polymerization and then to a total of78.6 g (5.5 g/mol reduced relative to the quantity of monomerintroduced) in the remainder of 290 minutes. The polymerizationtemperature was elevated at a rate of 1° C. per minute after thepolymerization was initiated at 30° C. and it was fixed at 90° C. afterthe elapse of 60 minutes following the initiation of polymerization.During each of the durations of dropwise addition, the relevantcomponent was continuously dropped at a fixed speed of dropping. In thecase of the 35% SBS, however, the speed of dropwise addition (fixed)during 10 minutes following the start of the polymerization and thespeed of dropwise addition (fixed) during the remainder of 290 minuteswere different.

After termination of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to age the solution andterminate the polymerization. After completion of the polymerization,the reaction solution was left cooling and then neutralized by having366.7 g (4.40 mols) of 48% NaOH gradually added dropwise thereto as keptstirred. Thus, an aqueous solution containing sodium polyacrylate havinga solid component concentration of 45 mass % and a final degree ofneutralization of 93 mol % (hereinafter referred to as “polymer (19)”)was obtained. The prescriptions for polymerization involved herein aresummarized in Table 4 below.

The polymer (19) consequently obtained was measured for molecularweight, value S, value R, value Q, iron ion concentration, Ca-bindingcapacity, quantity of gas, and quantity of precipitation at lowtemperature. The results are shown in Table 11.

Example 20

A polymer was obtained by following the procedure of Example 19(hereinafter referred to as “polymer 20”). The prescriptions for thepolymer are summarized in Table 4.

The polymer (20) consequently obtained was measured for molecularweight, value S, value R, value Q, iron ion concentration, Ca-bindingcapacity quantity of gas, and quantity of precipitation at lowtemperature. The results are shown in Table 11.

Example 21

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 154.0 g of purifiedwater was placed (initial charging) and stirred and nitrogen was blowntherein at a rate of 1 liter/min over a period of 30 minutes and theywere heated together to 30° C. To the reaction system of polymerizationthus obtained and continuously kept stirred, 427.5 g (4.75 mols) of 80%AA, 63.5 g (0.25 mol) of 37% SA, 66.7 g (2.0 g/mol as reduced relativeto the quantity of monomer introduced) of 15% NaPS, and 78.6 g (5.5g/mol as reduced relative to the quantity of monomer introduced) of 35%SBS were added dropwise through respectively independent droppingnozzles. The duration of dropwise addition was 300 minutes for the 80%AA, the 37% SA, and the 35% SBS each and 310 minutes for the 15% NaPS.In the case of the 35% SBS, however, it was added dropwise to a total of7.1 g (0.5 g/mol as reduced relative to the quantity of monomerintroduced) in 10 minutes following the start of the polymerization andthen to a total of 71.5 g (5.0 g/mol reduced relative to the quantity ofmonomer introduced) in the remainder of 290 minutes. The polymerizationtemperature was elevated at a rate of 0.5° C. per minute after thepolymerization was initiated at 30° C. and it was fixed at 90° C. afterthe elapse of 120 minutes following the initiation of polymerization.

After termination of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to age the solution andterminate the polymerization. After completion of the polymerization,the reaction solution was left cooling and then neutralized by having366.7 g (4.40 mols) of 48% NaOH gradually added dropwise thereto as keptstirred. Thus, an aqueous solution containing sodium polyacrylate havinga solid component concentration of 45 mass % and a final degree ofneutralization of 93 mol % (hereinafter referred to as “polymer (21)”)was obtained. The prescriptions for polymerization involved herein aresummarized in Table 4 below.

The polymer (21) consequently obtained was measured for molecularweight, value S, value R, value Q, Ca-binding capacity, quantity of gas,and quantity of precipitation at low temperature. The results are shownin Table 11.

Example 22

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 156.5 g of purifiedwater was placed (initial charging) and heated to 90° C. as kept in astirred state. To the resultant reaction system of polymerization whichwas kept stirred at a fixed temperature of about 90° C., 427.5 g (4.75mols) of 80% AA, 63.5 g (0.25 mol) of 37% SA, 66.7 g (2.0 g/mol asreduced relative to the quantity of monomer introduced) of 15% NaPS, and71.4 g (5.0 g/mol as reduced relative to the quantity of monomerintroduced) of 35% SBS were added dropwise through respectivelyindependent dropping nozzles. The duration of dropwise addition was 240minutes for the 80% AA, the 37% SA, and the 35% SBS each and 250 minutesfor the 15% NaPS.

After termination of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to terminate thepolymerization. After completion of the polymerization, nitrogen wasblown into the reaction solution at a rate of 1 liter/min over a periodof 30 minutes to expel sulfur dioxide from the reaction solution. Then,the reaction solution was left cooling. Thus, an aqueous solutioncontaining sodium polyacrylate having a solid component concentration of53 mass % and a final degree of neutralization of 5 mol % (hereinafterreferred to as “polymer (22)”) was obtained. The prescriptions forpolymerization involved herein are summarized in Table 5 below.

The polymer (22) consequently obtained was measured for molecularweight, value S, value R, value Q, iron ion concentration, Ca-bindingcapacity, quantity of gas, and quantity of precipitation at lowtemperature. The results are shown in Table 11.

Example 23

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 156.5 g of purifiedwater was placed (initial charging) and heated to 90° C. as kept in astirred state. To the reaction system of polymerization kept stirred ata fixed temperature of about 90° C., 427.5 g (4.75 mols) of 80% AA, 63.5g (0.25 mol) of 37% SA, 66.7 g (2.0 g/mol as reduced relative to thequantity of monomer introduced) of 15% NaPS, and 71.4 g (5.0 g/mol asreduced relative to the quantity of monomer introduced) of 35% SBS wereadded dropwise through respectively independent dropping nozzles. Theduration of dropwise addition was 240 minutes for the 80% AA, the 37%SA, and the 35% SBS each and 250 minutes for the 15% NaPS.

After termination of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to terminate thepolymerization. After completion of the polymerization, the reactionsolution was left cooling and measured for sulfur dioxide content, whichwas found to be 1.2 g. For the purpose of decreasing this sulfur dioxidecontent, 1.1 g (equimolar to sulfur dioxide component) of an aqueous 35%hydrogen peroxide solution (hereinafter abbreviated as “35% H₂O₂”) wasadded to the reaction solution. Thus, an aqueous solution containingsodium polyacrylate having a solid component concentration of 53 mass %and a final degree of neutralization of 5mol % (hereinafter referred toas “polymer (23)”) was obtained. The prescriptions for polymerizationinvolved herein are summarized in Table 5 below.

The polymer (23) consequently obtained was measured for molecularweight, value S, value R, value Q, iron ion concentration, Ca-bindingcapacity, quantity of gas, and quantity of precipitation at lowtemperature. The results are shown in Table 11.

Example 24

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 156.5 g of purifiedwater was placed (initial charging) and heated to 90° C. as kept in astirred state. Then, to the reaction system of polymerization keptstirred at a fixed temperature of about 90° C., 427.5 g (4.75 mols) of80% AA, 63.5 g (0.25 mol) of 37% SA, 66.7 g (2.0 g/mol as reducedrelative to the quantity of monomer introduced) of 15% NaPS, and 71.4 g(5.0 g/mol as reduced relative to the quantity of monomer introduced) of35% SBS were added dropwise through respectively independent droppingnozzles. The duration of dropwise addition was 240 minutes for the 80%AA, the 37% SA, and the 35% SBS each and 250 minutes for the 15% NaPS.

After termination of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to terminate thepolymerization. After completion of the polymerization, the reactionsolution was left cooling and then neutralized by having 366.7 g (4.40mols) of 48% NaOH gradually added dropwise thereto as kept stirred. Whenthe reaction solution was measured for sulfur dioxide content, thiscontent was found to be 1.8 g. For the purpose of decreasing this sulfurdioxide content, 1.7 g (equimolar to the sulfur dioxide content) of anaqueous 35% hydrogen peroxide solution was added. Thus, an aqueoussolution containing sodium polyacrylate having a solid componentconcentration of 45 mass % and a final degree of neutralization of 93mol % (hereinafter referred to as “polymer (24)”) was obtained. Theprescriptions for polymerization involved herein are summarized in Table5 below.

The polymer (24) consequently obtained was measured for molecularweight, value S, value R, value Q, iron ion concentration, Ca-bindingcapacity, quantity of gas, and quantity of precipitation at lowtemperature. The results are shown in Table 11.

TABLE 4 Example 18 19 20 21 Polymer (18) (19) (20) (21) Initial chargeof (g) 137.0 154.0 154.0 154.0 purified water 35% SBSaq (g) 7.1 0.0 0.00.0 (g/mol) 0.5 0.0 0.0 0.0 N₂ (L/min) 0.0 0.0 0.0 1.0 (min) 0 0 0 30Dropwise addition 80% AAaq (g) 405.0 427.5 427.5 427.5 (mol) 4.50 4.754.75 4.75 37% SAaq (g) 127.0 63.51 63.51 63.51 (mol) 0.50 0.25 0.25 0.2535% SBSaq (g) 85.7 85.7 78.6 78.6 (g/mol) 6.0 6.0 5.5 5.5 15% NaPSaq (g)66.7 66.7 66.7 66.7 (g/mol) 2.0 2.0 2.0 2.0 Duration of (min) dropwiseaddition 80% AAaq 0–240 0–300 0–300 0–300 37% SAaq 0–240 0–300 0–3000–300 35% SBSaq 0–240  0–300**  0–300**  0–300** 15% NaPSaq 0–250 0–3100–310 0–310 Polymerization (° C.) 30–90*   30–90***  30–90**** 30–90**** temperature Aging time (min) 30 30 30 30 Degree of (mol %)10.0 5.0 5.0 5.0 neutralization after dropwise addition After treatment48% NaOHaq (g) 333.3 366.7 366.7 366.7 (mol) 4.00 4.40 4.40 4.40 Finaldegree of (mol %) 90.0 93.0 93.0 93.0 neutralization PolymerizationSUS2.5L SUS2.5L SUS2.5L SUS2.5L Kettle Stirring vanes Paddle PaddlePaddle Paddle vanes vanes vanes vanes *After start of polymerization at30° C., the temperature was elevated at a rate of 1° C. per minute andfixed at 90° C. after elapse of 60 minutes following the start ofpolymerization. **35% SBS was added in a quantity of 0.5 g/mol in 0–10minutes and in the remainder of quantity in 10–300 minutes. ***Afterstart of polymerization at 30° C., the temperature was elevated at arate of 1° C. per minute and fixed at 90° C. after lapse of 60 minutesfollowing the start of polymerization. ****After start of polymerizationat 30° C., the temperature was elevated at a rate of 0.5° C. per minuteand fixed at 90° C. after lapse of 120 minutes following the start ofpolymerization.

TABLE 5 Example 22 23 24 Polymer (22) (23) (24) Initial charge of (g)156.5 156.5 156.5 purified water Dropwise addition 80% AAaq (g) 427.5427.5 427.5 (mol) 4.75 4.75 4.75 37% SAaq (g) 63.5 63.5 63.5 (mol) 0.250.25 0.25 35% SBSaq (g) 71.4 71.4 71.4 (g/mol) 5.0 5.0 5.0 15% NaPSaq(g) 66.7 66.7 66.7 (g/mol) 2.0 2.0 2.0 Duration of dropwise (min)addition 80% AAaq 0–240 0–240 0–240 37% SAaq 0–240 0–240 0–240 35% SBSaq0–240 0–240 0–240 15% NaPSaq 0–250 0–250 0–250 Polymerization (° C.) 9090 90 temperature Aging time (min) 30 30 30 Degree of (mol %) 5.0 5.05.0 neutralization after dropwise addition After treatment 48% NaOHaq(g) 0.0 0.0 366.7 (mol) 0.00 0.00 4.40 35% H₂O₂ (g) 0.0 1.1 1.7 (mol)0.000 0.012 0.017 N₂ (L/min) 1.0 0.0 0.0 (min) 30 0 0 Final degree of(mol %) 5.0 5.0 93.0 neutralization Polymerization SUS2.5L SUS2.5LSUS2.5L kettle Stirring vanes Paddle Paddle Paddle vanes vanes vanes

Example 25

In a separable flask made of SUS316, having an inner volume of 2.5liters, and provided with a reflux condenser and a stirrer, 185 g ofpurified water, 116 g (1 mol) of maleic anhydride (hereinafterabbreviated as “MA anhydride”), 16.7 g (0.2 mol) of an aqueous 48%sodium hydroxide solution (hereinafter abbreviated as “48% NaOH”) wereplaced and heated as stirred to 90° C. Then, 360 g (4 mols) of anaqueous 80% acrylic acid solution (hereinafter abbreviated as “80% AA”),33.3 g (0.4 mol) of 48% NaOH, 133.3 g (4 g/mol as reduced relative tothe quantity of monomer introduced) of an aqueous 15% sodium persulfatesolution (hereinafter abbreviated as “15% NaPS”), and 114.3 g (8 g/molas reduced relative to the quantity of monomer introduced) of an aqueous35% sodium bisulfite (hereinafter abbreviated as “35% SBS”) were addeddropwise to the stirred mixture in the flask through respectivelyindependent dropping ports. The duration of dropwise addition was 180minutes for the 80% AA, 185 minutes for the 48% NaOH, 185 minutes forthe 15% NaPS, and 175 minutes for the 35% SBS. The time for starting thedropwise addition was fixed for all the components. In this while, thetemperature was maintained at 90° C. This temperature was furthermaintained over 30 minutes after completion of the dropwise addition of80% AA to age the reaction solution and complete the polymerization.After completion of the polymerization, the reaction solution was leftcooling and then neutralized by the addition of 375 g (4.5 mols) of 48%NaOH thereto. Thus, an acrylic acid/maleic acid copolymer (25) having asolid component content of 45 mass % and a final degree ofneutralization of 85 mol % was obtained. The prescriptions for thepolymer and the molecular weight are summarized in Table 6.

Example 26

An acrylic acid/maleic acid copolymer (26) was obtained by following theprocedure of Example 25 while changing the prescriptions for the polymeras shown in Table 6. The prescriptions for the polymer and the molecularweight are summarized in Table 6.

Example 27

In a separable flask made of SUS316, having an inner volume of 2.5liters, and provided with a reflux condenser and a stirrer, 222 g ofpurified water was placed and heated as stirred to 90° C. Then, 116 g (1mol) of melted MA anhydride, 360 g (4 mols) of 80% AA, 50 g (0.6 mol) of48% NaOH, 133.3 g (4 g/mol as reduced relative to the quantity ofmonomer introduced) of 15% NaPS, and 114.3 g (8 g/mol as reducedrelative to the quantity of monomer introduced) of 35% SBS were addeddropwise to the stirred water in the flask through respectivelyindependent dropping ports. The duration of dropwise addition was 180minutes for the MA anhydride, 300 minutes for the 80% AA, 300 minutesfor the 48% NaOH, 310 minutes for the 15% NaPS, and 290 minutes for the35% SBS. The time for starting the dropwise addition was fixed for allthe components. In this while, the temperature was maintained at 90° C.This temperature was further maintained over 30 minutes after completionof the dropwise addition of 80% AA to age the reaction solution andcomplete the polymerization. After completion of the polymerization, thereaction solution was left cooling and then neutralized by the additionof 375 g (4.5 mols) of 48% NaOH thereto. Thus, an acrylic acid/maleicacid copolymer (27) having a solid component content of 45 mass % and afinal degree of neutralization of 85 mol % was obtained.Theprescriptions for the polymer and themolecular weight are summarizedin Table 6.

Example 28

In a separable flask made of SUS316, having an inner volume of 2.5liters, and provided with a reflux condenser and a stirrer, 208 g ofpurified water was placed and heated as stirred to 90° C. Then, 139 g(1.5 mols) of methacrylic acid (hereinafter abbreviated as “MAA”), 315 g(3.5 mols) of 80% AA, 20.8 g (0.25 mol) of 48% NaOH, 100 g (3 g/mol asreduced relative to the quantity of monomer introduced) of 15% NaPS, and85.7 g (6 g/mol as reduced relative to the quantity of monomerintroduced) of 35% SBS were added dropwise to the stirred mixture in theflask through respectively independent dropping ports. The duration ofdropwise addition was 180 minutes for MAA, 180 minutes for 80% AA, 180minutes for 48% NaOH, 185 minutes for 15% NaPS, and 175 minutes for 35%SBS. The time for starting the dropwise addition was fixed for all thecomponents. In this while, the temperature was maintained at 90° C. Thistemperature was further maintained over 30 minutes after completion ofthe dropwise addition of 80% AA to age the reaction solution andcomplete the polymerization. After completion of the polymerization, thereaction solution was left cooling and then neutralized by the additionof 375 g (4.5 mols) of 48% NaOH thereto. Thus, an acrylicacid/methacrylic acid copolymer (28) having a solid component content of45 mass % and a final degree of neutralization of 95 mol % was obtained.The prescriptions for the polymer and the molecular weight aresummarized in Table 7.

Example 29

In a separable flask made of SUS316, having an inner volume of 2.5liters, and provided with a reflux condenser and a stirrer, 114 g ofpurified water was placed and heated as stirred to 90° C. Then, 20.8 g(0.2 mol) of styrene (hereinafter a abbreviated as “St”), 342 g (3.8mols) of 80% AA, 15.8 g (0.19 mol) of 48% NaOH, 106.7 g (4 g/mol asreduced relative to the quantity of monomer introduced) of 15% NaPS,91.4 g (8 g/mol as reduced relative to the quantity of monomerintroduced) of 35% SBS, and 5.2 g of purified water were added dropwiseto the stirred mixture in the flask. While the purified water was addedas mixed with 80% AA, the other components were added dropwise throughrespectively independent dropping ports. The duration of dropwiseaddition was 150 minutes for the St, 180 minutes for the 80% AA, 180minutes for the 48% NaOH, 190 minutes for the 15% NaPS, and 180 minutesfor the 35% SBS. The time for starting the dropwise addition was fixedfor all the components. In this while, the temperature was maintained at90° C. This temperature was further maintained over 30 minutes aftercompletion of the dropwise addition of 80% AA to age the reactionsolution and complete the polymerization. After completion of thepolymerization, the reaction solution was left cooling and thenneutralized by the addition of 285 g (3.42 mols) of 48% NaOH thereto.Thus, an acrylic acid/styrene copolymer (29) having a solid componentcontent of 45 mass % and a final degree of neutralization of 95 mol %was obtained. The prescriptions for the polymer and the molecular weightare summarized in Table 8.

Example 30

In a separable flask made of SUS316, having an inner volume of 2.5liters, and provided with a reflux condenser and a stirrer, 145 g ofpurified water was placed and heated as stirred to 90° C. Then, 43 g(0.5 mol) of methyl acrylate (hereinafter abbreviated as “AM”), 405 g(4.5 mols) of 80% AA, 18.8 g (0.23 mol) of 48% NaOH, 133.3 g (4 g/mol asreduced relative to the quantity of monomer introduced) of 15% NaPS,114.3 g (8 g/mol as reduced relative to the quantity of monomerintroduced) of 35% SBS, and 10.8 g of purified water were added dropwiseto the stirred water in the flask. While the purified water was addeddropwise as mixed with the 80% AA, the other components were addeddropwise through respectively independent dropping ports. The durationof dropwise addition was 180 minutes for the AM, 180 minutes for the 80%AA and the purified water, 180 minutes for the 48% NaOH, 185 minutes forthe 15% NaPS, and 175 minutes for the 35% SBS. The time for starting thedropwise addition was fixed for all the components. In this while, thetemperature was maintained at 90° C. This temperature was furthermaintained over 30 minutes after completion of the dropwise addition of80% AA to age the reaction solution and complete the polymerization.After completion of the polymerization, the reaction solution was leftcooling and then neutralized by the addition of 337.5 g (4.05 mols) of48% NaOH thereto. Thus, an acrylic acid/methyl acrylate copolymer (30)having a solid component content of 45 mass % and a final degree ofneutralization of 95 mol % was obtained. The prescriptions for thepolymer and the molecular weight are summarized in Table 9.

TABLE 6 Example 25 26 27 Polymer (25) (26) (27) Initial charge of (g)116.0 58.0 0.0 MA anhydride (mol) 1.0 0.5 0.0 48% NaOH (g) 16.7 4.2 0.0(mol) 0.2 0.2 0.0 Purified water (g) 185.0 198.0 222.0 Dropwise additionMA anhydride (g) 0.0 0.0 116.0 (mol) 0.0 0.0 1.0 80% AA (g) 360.0 405.0360.0 (mol) 4.0 4.5 4.0 48% NaOH (g) 33.3 18.8 50.0 (mol) 0.4 0.225 0.615% NaPS (g) 133.3 133.3 133.3 (g/mol) 4.0 4.0 4.0 35% SBS (g) 114.3114.3 114.3 (g/mol) 8.0 8.0 8.0 Duration of (min) dropwise addition MAanhydride — — 0–180 80% AA 0–180 0–180 0–300 48% NaOH 0–180 0–180 0–30015% NaPS 0–175 0–175 0–290 35% SBS 0–185 0–185 0–310 Polymerization (°C.) 90 90 90 and aging temperature Aging time (min) 30 30 30 Degree of(mol %) 10 5 10 neutralization after dropwise addition After treatment48% NaOH (g) 375.0 366.7 375.0 (mol) 4.5 4.4 4.5 Final degree of (mol %)85.0 85.0 85.0 neutralization Polymerization SUS2.5L SUS2.5L SUS2.5Lkettle Stirring vanes Paddle Paddle Paddle vanes vanes vanes Molecularweight Mw 9700 9400 7800 Mn 2900 2200 2400

TABLE 7 Example 28 Polymer (28) Initial charge of (g) 208.0 purifiedwater Dropwise addition MAA (g) 129.0 (mol) 1.5 80% AA (g) 315.0 (mol)3.5 48% NaOH (g) 20.8 (mol) 0.25 15% NaPS (g) 100.0 (g/mol) 3.0 35% SBS(g) 85.7 (g/mol) 6.0 Duration of (min) dropwise addition MAA 0–180 80%AA 0–180 48% NaOH 0–180 15% NaPS 0–185 35% SBS 0–175 Polymerization and(° C.) 90 aging temperature Aging time (min) 30 Degree of (mol %) 5neutralization after dropwise addition After treatment 48% NaOH (g)375.0 (mol) 4.5 Final degree of (mol %) 95.0 neutralizationPolymerization SUS2.5L kettle Stirring vanes Paddle vanes Molecularweight Mw 6600 Mn 2600

TABLE 8 Example 29 Polymer (29) Initial charge of (g) 114.0 purifiedwater Dropwise addition St (g) 20.8 (mol) 0.2 80% AA (g) 342.0 (mol) 3.848% NaOH (g) 15.8 (mol) 0.19 Purified water (g) 5.2 15% NaPS (g) 106.7(g/mol) 4.0 35% SBS (g) 91.4 (g/mol) 8.0 Duration of dropwise (min)addition St 0–150 80% AA 0–180 48% NaOH 0–180 Purified water 0–180 15%NaPS 0–190 35% SBS 0–180 Polymerization and (° C.) 90 aging temperatureAging time (min) 30 Degree of (mol %) 5 neutralization after dropwiseaddition After treatment 48% NaOH (g) 285.0 (mol) 3.42 Final degree of(mol %) 95.0 neutralization Polymerization SUS2.5L kettle Stirring vanesPaddle vanes Molecular weight Mw 8500 Mn 2600

TABLE 9 Example 30 Polymer (30) Initial charge of (g) 145.0 purifiedwater Dropwise addition AM (g) 43.0 (mol) 0.5 80% AA (g) 405.0 (mol) 4.548% NaOH (g) 18.8 (mol) 0.23 Purified water (g) 10.8 15% NaPS (g) 133.3(g/mol) 4.0 35% SBS (g) 114.3 (g/mol) 8.0 Duration of dropwise (min)addition AM 0–180 80% AA 0–180 48% NaOH 0–180 purified water 0–180 15%NaPS 0–185 35% SBS 0–175 Polymerization and (° C.) 90 aging temperatureAging time (min) 30 Degree of (mol %) 5 neutralization after dropwiseaddition After treatment 48% NaOH (g) 337.5 (mol) 4.05 Final degree of(mol %) 95.0 neutralization Polymerization SUS2.5L kettle Stirring vanesPaddle vanes Molecular weight Mw 3600 Mn 1500

Comparative Example 1

In a separable flask made of SUS, having an inner volume of 5 liters,and provided with a reflux condenser and a stirrer, 350 g of purifiedwater was placed (initial charging) and heated as stirred to the boilingpoint. Then, 900 g (10 mols) of 80% AA, 266.7 g (4.0 g/mol as reducedrelative to the quantity of monomer introduced) of 15% NaPS, 228.6 g(8.0 g/mol as reduced relative to the quantity of monomer introduced) of35% SBS, and 83.3 g (1 mol) of 48% NaOH were added dropwise to thereaction system of polymerization kept stirred in a refluxed state atthe boiling point through respectively independent dropping nozzles. Theduration of dropwise addition was 180 minutes for the 80% AA and the 48%NaOH, and 190 minutes for the 15% NaPS and the 35% SBS. The componentswere each added dropwise at a fixed speed continuously throughout therelevant length of dropwise addition.

After completion of the dropwise addition, the reaction solution wasfurther retained at the boiling point over a period of 30 minutes to agethe reaction solution and complete the polymerization. After completionof the polymerization, the reaction solution was left cooling and thenneutralized by having 225 g (2.7 mols) of 48% NaOH gradually addeddropwise as stirred thereto. Thus, an aqueous solution containing sodiumpolyacrylate having a solid component concentration of 45 mass % and afinal degree of neutralization of 37 mol % (hereinafter referred to as“Comparative polymer (1)).” The prescriptions for the polymer aresummarized in Table 10 below.

The comparative polymer (1) consequently obtained was measured formolecular weight, value S, value R, value Q, iron ion concentration,Ca-binding capacity, quantity of gas, and quantity of precipitation atlow temperature. The results are shown in Table 11 below.

Comparative Example 2

In a separable flask made of SUS, having an inner volume of 5 liters,and provided with a reflux condenser and a stirrer, 150 g of purifiedwater was placed (initial charging) and heated as stirred to the boilingpoint. Then, 900 g (10 mols) of 80% AA, 266.7 g (4.0 g/mol as reducedrelative to the quantity of monomer introduced) of 15% NaPS, 228.6 g(8.0 g/mol as reduced relative to the quantity of monomer introduced) of35% SBS, and 11.4 g of purified water were added dropwise invariablyover a period of 120 minutes to the reaction system of polymerizationkept stirred in a refluxed state at the boiling point throughrespectively independent dropping nozzles. The components were eachadded dropwise at a fixed speed continuously throughout the relevantlength of dropwise addition.

After completion of the dropwise addition, the reaction solution wasfurther retained at the boiling point over a period of 30 minutes to agethe reaction solution and complete the polymerization. After completionof the polymerization, the reaction solution was left cooling and thenneutralized by having 750 g (9.0 mols) of 48% NaOH gradually addeddropwise as stirred thereto. Thus, an aqueous solution containing sodiumpolyacrylate having a solid component concentration of 45 mass % and afinal degree of neutralization of 90 mol % (hereinafter referred to as“Comparative polymer (2)).” The prescriptions for the polymer aresummarized in Table 10 below.

The comparative polymer (2) consequently obtained was measured formolecular weight, value S, value R, value Q, iron ion concentration,Ca-binding capacity, quantity of gas, and quantity of precipitation atlow temperature. The results are shown in Table 11 below.

Comparative Example 3

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 133.5 g of purifiedwater was placed (initial charging) and heated as stirred to the boilingpoint. Then, 405.0 g (4.50 mols) of 80% AA, 127.0 g (0.50 mol) of 37%SA, 66.7 g (2.0 g/mol as reduced relative to the quantity of monomerintroduced) of 15% NaPS, and 85.7 g (6.0 g/mol as reduced relative tothe quantity of monomer introduced) of 35% SBS were added dropwise tothe reaction system of polymerization kept stirred in a refluxed stateat the boiling point through respectively independent dropping nozzles.The duration of dropwise addition was 240 minutes for the 80% AA, the37% SA, and the 35% SBS and 250 minutes for the 15% NaPS.

After completion of the dropwise addition, the reaction solution wasfurther retained at the boiling point over a period of 30 minutes to agethe reaction solution and complete the polymerization. After completionof the polymerization, the reaction solution was left cooling and thenneutralized by having 345.8 g (415 mols) of 48% NaOH gradually addeddropwise as stirred thereto. Thus, an aqueous solution containing sodiumpolyacrylate having a solid component concentration of 45 mass % and afinal degree of neutralization of 93 mol % (hereinafter referred to as“Comparative polymer (3)).” The prescriptions for the polymer aresummarized in Table 10 below.

The comparative polymer (3) consequently obtained was measured formolecular weight, value S, value R, value Q, iron ion concentration,Ca-binding capacity, quantity of gas, and quantity of precipitation atlow temperature. The results are shown in Table 11 below.

Comparative Example 4

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 635.3 g of purifiedwater was placed (initial charging) and heated as stirred to the boilingpoint. Then, 762.5 g (3.0 mols) of 37% SA, 24.0 g (1.2 g/mol as reducedrelative to the quantity of monomer introduced) of 15% NaPS, and 82.3 gof purified water were added dropwise to the reaction system ofpolymerization kept stirred in a refluxed state at the boiling pointthrough respectively independent dropping nozzles. The duration ofdropwise addition was 200 minutes for the 37% SA and 205 minutes for the15% NaPS and the purified water.

After completion of the dropwise addition, the reaction solution wasfurther retained at the boiling point over a period of 30 minutes to agethe reaction solution and complete the polymerization. After completionof the polymerization, the reaction solution was left cooling. Thus, anaqueous solution containing sodium polyacrylate having a solid componentconcentration of 20 mass % and a final degree of neutralization of 100mol % (hereinafter referred to as “Comparative polymer (4)).” Theprescriptions for the polymer are summarized in Table 10 below.

The comparative polymer (4) consequently obtained was measured formolecular weight, value S, value R, value Q, iron ion concentration,Ca-binding capacity, quantity of gas, and quantity of precipitation atlow temperature. The results are shown in Table 11 below.

TABLE 10 Comparative Example 1 2 3 4 Comparative (1) (2) (3) (4) polymerInitial charge Purified water (g) 350.0 150.0 133.5 635.3 35% SBSaq (g)0.0 0.0 0.0 0.0 (g/mol) 0.0 0.0 0.0 0.0 Dropwise addition 80% AAaq (g)900.0 900.0 427.5 0.0 (mol) 10.0 10.0 4.75 0.0 37% SAaq (g) 0.0 0.063.51 762.5 (mol) 0.0 0.0 0.25 3 35% SBSaq (g) 228.6 228.6 85.7 0.0(g/mol) 8.0 8.0 6.0 0.0 15% NaPSaq (g) 266.7 266.7 66.7 24 (g/mol) 4.04.0 2.0 1.2 48% NaOHaq (g) 83.3 0.0 0.0 0.0 (g/mol) 1.0 0.0 0.0 0.0Purified water (g) 0.0 11.4 0.0 82.3 Duration of (min) dropwise addition80% AAaq 0–180 0–120 0–240 — 37% SAaq — — 0–240 0–200 35% SBSaq 0–1900–120 0–240 — 15% NaPSaq 0–190 0–120 0–250 0–205 48% NaOHaq 0–180 — — —Purified water — 0–120 — 0–205 Polymerization (° C.) 100 100 100 100temperature (boiling (boiling (boiling (boiling point) point) point)point) Aging time (min) 30 30 30 30 Degree of (mol %) 10 0 0 100neutralization after dropwise addition After treatment 48% NaOHaq (g)225.0 750.0 345.8 0 (mol) 2.7 9.0 15.0 0 Final degree of (mol %) 37.090.0 93.0 100 neutralization Polymerization SUS5L SUS5L SUS2.5L SUS2.5Lkettle Stirring vanes Paddle Paddle Paddle Paddle vanes vanes vanesvanes

TABLE 11 Ca- Quantity of Molecular Quantity Anti-gelling Fe bindingQuantity precipitation weight of S NMR ability concentration ability ofgas at low Mw/Mn Values S Values R Values Q (ppm) (mgCaCo₃/g) (L)temperature Polymer (1) 5800/2400 49 5.0 2.02 1.40 250 ≦0.3 a littlePolymer (2) 2500/1200 43 8.3 1.85 1.56 220 ≦0.3 a little Polymer (3)4100/1500 40 6.1 2.01 1.83 236 ≦0.3 a little Polymer (4) 3200/1600 447.5 2.05 1.46 224 ≦0.3 a little Polymer (5) 4700/2000 45 5.9 2.01 1.23239 ≦0.3 a little Polymer (6) 3900/1800 46 6.2 1.99 0.98 232 ≦0.3 alittle Polymer (7) 6200/2600 46 3.9 2.23 1.53 244 ≦0.3 a little Polymer(8) 6200/2800 45 5.8 2.21 1.85 242 ≦0.3 a little Polymer (9) 8100/320038 4.4 2.39 1.76 262 ≦0.3 a little Polymer (10) 4700/2100 46 4.8 2.182.02 242 ≦0.3 a little Polymer (11) 8200/3000 43 5.1 2.37 1.65 260 ≦0.3a little Polymer (12) 6000/2400 47 5.0 2.06 1.73 248 ≦0.3 a littlePolymer (13) 7600/2600 44 1.9 2.33 1.98 257 ≦0.3 a little Polymer (14)5900/2400 44 4.5 2.23 1.76 251 ≦0.3 a little Polymer (15) 4800/2100 423.2 2.22 0.83 240 ≦0.3 a little Polymer (16) 4700/2000 43 4.3 2.30 1.77240 ≦0.3 a little Polymer (17) 7800/2800 39 5.5 2.30 0.95 259 ≦0.3 alittle Polymer (18) 5500/2400 43 5.6 2.24 1.23 243 ≦0.3 a little Polymer(19) 5800/2800 42 4.5 2.31 0.78 249 ≦0.3 a little Polymer (20) 6500/240040 4.2 2.25 1.45 252 ≦0.3 a little Polymer (21) 6300/2400 44 4.1 2.180.49 250 ≦0.3 a little Polymer (22) 6000/2400 47 3.9 2.19 1.56 255 ≦0.3a little Polymer (23) 5900/2400 49 5.5 2.22 1.37 251 ≦0.3 a littlePolymer (24) 6000/2500 47 6.3 2.23 1.11 254 ≦0.3 a little Comparative6600/2200 30 4.8 1.38 1.89 231 3.9 much polymer (1) Comparative7200/2400 32 3.3 1.51 1.95 234 4.3 much polymer (2) Comparative23000/5000 25 2.3 1.04 2.03 266 2.6 much polymer (3) Comparative4800/2100 0 0.0 3.92 0.40 250 ≦0.3 a little polymer (4)

The Ca-binding capacity in Table 11 tends to increase in accordance asthe molecular weight increases. The results of this quality must betherefore compared between samples having about equal molecular weights.As concerns the results shown in Table 11, while the polymer (20) andthe comparative polymer (1) are samples of nearly equal molecularweights, the Ca-binding capacity is 252 for the polymer (20) and 231 forthe comparative polymer (1), i.e. the polymer (20) clearly excels thecomparative polymer (1). It is noteworthy that while the polymer (16),for example, excels in the Ca-binding capacity notwithstanding it has afairly small molecular weight as compared with the comparative polymer(1).

Incidentally, this polymer has a large value Q representing theanti-gelling ability (namely the anti-gelling ability is lowered), ascompared with the comparative polymers (1) and (2). This fact may belogically explained by the following postulate.

The anti-gelling ability, on account of the nature of evaluation, tendsto decline in accordance as the polymer concentration increases. Thepolymer in the working examples of this invention which has succeeded inmarkedly decreasing the impurity content, therefore, inevitably exhibitspoor anti-gelling ability as compared with the comparative polymers (1)and (2) which have large impurity contents (referred to the data ofquantity of precipitate at low temperature, value S, and Ca-bindingcapacity regarding this point). The results under discussion, therefore,do not necessarily imply that the polymers of this invention areinferior in the anti-gelling ability.

<Regarding Unsaturated Polyalkylene Glycol Type Copolymer>

The unsaturated polyalkylene glycol type copolymers produced accordingto this invention were measured or determined for (2-1) the quantity Scontained in a given polymer and the total quantity S and the method ofdialysis used for their determination, (2-2) the weight averagemolecular weight (Mw) and the number average molecular weight (Mn),(2-3) the degree of gelation to be used for finding the anti-gellingability, (2-4) the hue (value b), (2-5) the Ca-binding capacity, (2-6)the clay dispersing ability, and (2-7) the compatibility with a liquiddetergent by the methods shown below.

Of these items, (2-1) and (2-3) were rated by following the procedureused in the working examples producing such (meth)acrylic acid typepolymers as mentioned above. That is, they are equal respectively to(1-1) and (1-3) excepting that unsaturated polyalkylene glycol typecopolymers are used instead of (meth)acrylic acid type polymers.

(2) Measurement of Weight Average Molecular Weight (Mw) and NumberAverage Molecular Weight (Mn)

The weight average molecular weight (Mw) and the number averagemolecular weight (Mn) of a given unsaturated polyalkylene glycol typecopolymer were both measured by means of GPC (gel permeationchromatography). The conditions and the devices used for the measurementwere as follows.

-   Device: Product of Hitachi, Ltd. sold under the product code of    “L-7000 series”-   Detector: RI-   Column: Products of Shodex Corp. sold under product codes of “SB-G”,    “SB-804”, “SB-803”, “SB-802.5”-   Column temperature: 40° C.-   Calibration curve: Product of Sowa Kagaku K.K. sold under the    trademark designation of Polyacrylic Acid Standard GPC software:    Product of Nippon Bunko K.K. sold under the trademark designation of    “BORWIN”-   Eluent: 0.1M phosphate buffer (pH 8.0)/acetonitrile=9/1 (weight    ratio)

(4) Hue (Value b)

A given polymer or an aqueous polymer solution was diluted orconcentrated till a polymer concentration of 40 mass %. By testing theprepared aqueous solution for transmittance by the use of a calorimetermade by Nippon Denshoku Kogyo K.K. and sold under the product code of“ND-1001DP” to find the laboratory grade value b. The value b is suchthat the yellow color of a given aqueous solution gains in density inaccordance as the magnitude of the value b increase in the direction ofpositive number.

(5) Measurement of Ca-Binding Capacity

As the calcium ion standard solutions for the calibration curve, aqueoussolutions were prepared using calcium chloride dihydrate each in a fixedquantity of 50 g respectively at concentrations of 0.01 mol/liter, 0.001mol/liter and 0.0001 mol/liter. They were adjusted to pH values in therange of 9–11 with an aqueous 4.8% NaOH solution and further werethoroughly stirred together with 1 ml of an aqueous 4 mol/literpotassium chloride solution (hereinafter abbreviated as “4M-KCl aqueoussolution”) added thereto by the use of a magnetic stirrer to preparesample solutions for the calibration curve. As the calcium ion standardsolutions for the testing, aqueous 0.001 mol/liter calcium chloridedihydrate solutions were prepared in a necessary quantity (50 g persample).

Then, in a 100-ml beaker, a test sample (polymer) weighed out in aquantity of 10 mg as reduced to a solid component content was placed andthen thoroughly stirred together with 50 g of the aforementioned calciumion standard solution for the testing by means of a magnetic stirrer.Further, similarly to the calibration curve sample, the resultantsolution was adjusted to a pH in the range of 9–11 with an aqueous 4.8%NaOH solution and made to produce a testing sample solution by theaddition of 1 ml of an aqueous 4M-KCl solution.

The calibration curve sample solutions and the testing sample solutionsthus prepared were assayed with a calcium ion electrode 93-20 and areference electrode 90-01, both made by Orion K.K. in a titrating devicemade by Hiranuma Sangyo K.K. and sold under the trademark designation of“COMTITE-550.”

The quantity of calcium ion binded by a given sample (polymer) was foundby calculation using the values found consequently of the samplesolutions for the calibration curve and for the testing. This quantity,i.e. the quantity of the binded calcium ion per g of the solid contentof the relevant polymer, was expressed in the number of mg as reduced tocalcium carbonate. This quantity was reported as the value of Ca-bindingcapacity.

(6) Clay Dispersing Property

A buffer was prepared by diluting 67.56 g of glycine, 52.6 g of sodiumchloride, and 2.4 g of NaOH with purified water to give a total weightof 600 g. Sixty (60) g of the buffer and 0.3268 g of calcium chloridedihydrate were added together and were further purified water was addedto give a total weight of 1000 g (to be used as a buffer). Four (4) g(reduced to a weight of a solid component) of an aqueous 0.1 mass %solution of a given copolymer and 36 g of the buffer added thereto werestirred together to form a dispersion. In a test tube measuring 18 mm indiameter and 180 mm in height (made by Iwaki Glass K.K.), 0.3 g of clay(made by Nippon Funtai Kogyo Gijutsu Kyokai Corp. and sold under theproduct code of “Testing Dust Type 8”) was placed and then 30 g of thedispersion mentioned above was added thereto and they are togethersealed in the test tube.

The test tube was shaken till the clay was uniformly dispersed.Thereafter, the test tube was left standing at rest in a dark place for20 hours. At the end of the 20 hours' standing, 5 ml of the supernatantof the dispersion was taken and tested for absorbency with an UVspectroscope using a 1-cm cell and a wavelength of 380 nm (made byShimadzu Seisakusho K.K. and sold under the product code of “UV-1200”).The larger the absorbency is, the higher the clay dispersing propertyis.

(7) Compatibility with Liquid Detergent

Detergents containing novel copolymers obtained in the following workingexamples were rated for compatibility with a liquid detergent.

Various detergents were prepared by using novel copolymers obtained inthe working examples and the following components. These materials werethoroughly stirred till the relevant components were uniformly blendedand the resultant samples were tested for turbidity at 25° C. Aturbidometer made by Nippon Denshoku K.K. and sold under the productcode of “NDH2000” was used for the measurement of the turbidity (kaolinturbidity mg/liter).

The results were rated on the following three-point scale, wherein

∘: Value of turbidity (0–50 (mg/liter)), absence of a visuallydiscernible sign of separation, sedimentation, or cloudiness.

Δ: Value of turbidity (50–200 (mg/liter)), presence of a visuallydiscernible sign of slight cloudiness

x: Value of turbidity (not less than 200 (mg/liter) presence of avisually discernible sign of cloudiness

Formulation of detergent:

-   -   SFT-70H (Softanol 70H polyoxyethylene alkyl ether, made by        Nippon Shokubai Co., Ltd.); 11 g Neopelex F-65 (sodium        dodecylbenzene sulfonate made by Kao Corporation): 32 g    -   Diethanol amine: 10 g    -   Ethanol; 5 g    -   Propylene glycol; 15 g    -   A novel copolymer and a comparative polymer obtained in        examples; 1.5 g (each)    -   Water; Balance

Example 31

In a separable flask made of SUS, having an inner volume of 2.5 liters,and provided with a reflux condenser and a stirrer, 145.0 g of purifiedwater was placed (initial charging) and heated as stirred to 90° C.

Then, 180.0 g (2.00 mols) of an aqueous 80% acrylic acid solution(hereinafter abbreviated as “80% AA”), 8.33 g (0.10 mol) of 48% sodiumhydroxide (hereinafter abbreviated as “48% NaOH”), 328.8 g (0.50 mol) ofan unsaturated alcohol resulting from adding 10 mols of ethylene oxideto 80% 3-methyl-3-buten-1-ol (hereinafter referred to as “80% IPN-10”),66.7 g (4.0 g/mol as reduced to the quantity of monomer introduced(wherein the expression “quantity of monomer introduced” as used hereinmeans the quantity of all the monomers introduced; which similarlyapplies hereinafter) of an aqueous 15% sodium persulfate solution(hereinafter abbreviated as “15% NaPS”), 57.1 g (8.0 g/mol as reducedrelative to the quantity of monomer introduced) of an aqueous 35% sodiumbisulfite solution (hereinafter abbreviated as “35% SBS”), and 100 g ofpurified water were added dropwise to the reaction system ofpolymerization kept stirred at a fixed temperature of about 90° C.through respectively independent dropping nozzles. The duration ofdropwise addition was 180 minutes for the 80% AA and the 48% NaOH, 170minutes for the 80% IPN-10, 175 minutes for the 35% SBS, and 210 minutesfor the 15% NaPS and the purified water. The components were eachcontinuously added dropwise at a fixed speed throughout the entirelength of dropwise addition.

After completion of the dropwise addition, the reaction solution wasretained at 90° C. over a period of 30 minutes to age the reactionsolution and complete the polymerization. After completion of thepolymerization, the reaction solution was left cooling and thenneutralized by having 75.0 g (0.90 mol) of an aqueous 48% sodiumhydroxide solution gradually added dropwise to the reaction solution ina stirred state. Thus, an unsaturated polyalkylene glycol type copolymerhaving a solid component concentration of 45 mass % and a final degreeof neutralization of 50 mol % (hereinafter referred to “polymer (31)”).The prescriptions for the polymer are summarized in Table 12 below.

The polymer (31) consequently obtained was measured for molecularweight, value S, value b, value q or value Q, Ca-binding capacity, claydispersing ability, and compatibility with a liquid detergent. Theresults are shown in Tables 18 and 20 below.

Examples 32–39

Polymers (32)–(39) were obtained by following the procedure of Example31. The prescriptions for the polymers are summarized in Tables 12 and13 below.

The polymers (32)–(39) consequently obtained were measured each formolecular weight, value S, value b, value q or value Q, Ca-bindingcapacity, clay dispersing ability, and compatibility with a liquiddetergent. The results are shown in Tables 18 and 20 below.

TABLE 12 Example 31 32 33 34 35 Polymer (31) (32) (33) (34) (35) Initialcharge of (g) 250.0 230.0 255.0 200.0 145.0 purified water Dropwiseaddition 80% AAaq (g) 180.0 360.0 342.0 342.0 243.7 (mol) 2.00 4.00 3.803.80 2.71 80% IPN-10 (g) 328.8 90.1 131.5 131.5 131.2 (mol) 0.50 0.140.20 0.20 0.20 48% NaOHaq (g) 8.33 16.67 15.83 15.83 11.28 (mol) 0.100.20 0.19 0.19 0.14 35% SBSaq (g) 57.1 94.6 91.4 57.1 41.5 (g/mol) 8.08.0 8.0 5.0 5.0 15% NaPSaq (g) 66.7 110.3 106.7 106.7 96.9 (g/mol) 4.04.0 4.0 4.0 5.0 Water (g) 100.0 0.0 0.0 60.0 60.0 Duration of dropwise(min) addition 80% AAaq 0–180 0–180 0–180 0–180 0–180 80% IPN-10 0–1700–170 0–170 0–180 0–180 80% NaOHaq 0–180 0–180 0–180 0–180 0–180 35%SBSaq −10–180    −10–180    −10–180    0–170 0–170 15% NaPSaq 0–2100–210 0–210 0–210 0–240 Water 0–↑ — — 0–↑ 0–↑ Polymerization and (° C.)90 90 90 90 90 ageing temperature (min) 30 30 30 30 30 Aging time Degreeof (%) 5.0 5.0 5.0 5.0 5.0 neutralization after dropwise addition Aftertreatment 48% NaOHaq (g) 75.0 150.0 142.5 142.5 101.5 (mol) 0.90 1.801.71 1.71 1.22 Final degree of (%) 50.0 50.0 50.0 50.0 50.0neutralization Charged solid (%) 43.06 43.14 43.19 43.25 43.17 componentPolymerization SUS2.5L SUS2.5L SUS2.5L SUS2.5L SUS2.5L kettle Stirringvanes Paddle Paddle Paddle Paddle Paddle vanes vanes vanes vanes vanesFinal charge (g) 1065.89 1051.62 1084.93 1055.64 831.20

TABLE 13 Example 36 37 38 39 Polymer (36) (37) (38) (39) Initial chargeof (g) 240.0 340.0 140.0 155.0 purified water Dropwise addition 80% AAaq(g) 250.0 342.0 243.7 295.9 (mol) 2.78 3.80 2.71 3.29 80% IPN-10 (g)250.0 131.5 131.2 32.9 (mol) 0.38 0.20 0.20 0.05 48% NaOHaq (g) 11.5715.83 11.28 13.70 (mol) 0.14 0.19 0.14 0.16 35% SBSaq (g) 45.1 57.1 66.576.3 (g/mol) 5.0 5.0 8.0 8.0 15% NaPSaq (g) 105.3 106.7 96.9 89.0(g/mol) 5.0 4.0 5.0 4.0 Water (g) 60.0 60.0 60.0 0.0 Duration ofdropwise (min) addition 80% AAaq 0–180 0–180 0–180 0–180 80% IPN-100–180 0–180 0–180 0–180 80% NaOHaq 0–180 0–180 0–180 0–180 35% SBSaq0–170 0–170 0–180 0–180 15% NaPSaq 0–240 0–210 0–240 0–210 Water 0–↑ 0–↑0–↑ — Polymerization and (° C.) 90 90 90 90 ageing temperature Agingtime (min) 30 30 30 30 Degree of (%) 5.0 5.0 5.0 5.0 neutralizationafter dropwise addition After treatment 48% NaOHaq (g) 104.2 142.5 101.5123.3 (mol) 1.25 1.71 1.22 1.48 Final degree of (%) 50.0 50.0 50.0 50.0neutralization Charged solid component (%) 43.35 38.19 43.18 43.15Polymerization kettle SUS2.5L SUS2.5L SUS2.5L SUS2.5L Stirring vanesPaddle Paddle Paddle Paddle vanes vanes vanes vanes Final charge (g)1066.12 1195.64 851.12 786.07

Examples 40–42

Polymers (40)–(42) were obtained by following the procedure of Example31 while using an unsaturated alcohol resulting from the addition of 50mols of ethylene oxide to 50% 3-methyl-3-buten-1-ol (hereinafterreferred to as “50% IPN-50”) in place of the 80% IPN-10. Theprescriptions for the polymers are summarized in Table 14 below.

The polymers (40)–(42) consequently obtained were each tested formolecular weight, value S, value b, value q or value Q, Ca-bindingcapacity, clay dispersing ability and compatibility with a liquiddetergent. The results are shown in Tables 18 and 20 below.

TABLE 14 Example 40 41 42 Polymer (40) (41) (42) Initial charge of (g)151.0 145.0 238.0 purified water Dropwise addition 80% AAaq (g) 300.0270.0 450.0 (mol) 3.33 3.00 5.00 50% IPN-50 (g) 120.0 168.0 80.0 (mol)0.03 0.04 0.02 48% NaOHaq (g) 13.89 12.50 20.83 (mol) 0.17 0.15 0.25 35%SBSaq (g) 76.8 69.4 86.0 (g/mol) 8.0 8.0 6.0 15% NaPSaq (g) 89.6 81.0100.3 (g/mol) 4.0 4.0 3.0 Water (g) 0.0 0.0 0.0 Duration of dropwise(min) addition 80% AAaq 0–180 0–180 0–180 50% IPN-50 0–120 0–120 0–15080% NaOHaq 0–180 0–180 0–180 35% SBSaq 0–180 0–180 0–180 15% NaPSaq0–210 0–210 0–210 Water Polymerization and (° C.) 90 90 90 ageingtemperature Aging time (min) 30 30 30 Degree of (%) 5.0 5.0 5.0neutralization after dropwise addition After treatment 48% NaOHaq (g)124.9 112.5 187.5 (mol) 1.50 1.35 2.25 Final degree of (%) 50.0 50.050.0 neutralization Charged solid (%) 43.02 43.04 43.02 componentPolymerization SUS2.5L SUS2.5L SUS2.5L kettle Stirring vanes PaddlePaddle Paddle vanes vanes vanes Final charge (g) 876.18 858.39 1162.70

Example 43

A polymer was obtained by following the procedure of Example 31 whileusing an unsaturated alcohol resulting from adding 5 mols of ethyleneoxide to 80% allyl alcohol in place of the 80% IPN-10 (hereinafterreferred to as “80% PEA A-5”). The prescriptions for this polymer aresummarized in Table 15 blow.

The polymer (43) consequently obtained was measured for molecularweight, value S, value b, value q or value Q, Ca-binding capacity,dispersing ability, and compatibility with a liquid detergent. Theresults are shown in Tables 18 and 20 below.

TABLE 15 Example 43 Polymer (43) Initial charge of (g) 270.0 purifiedwater Dropwise addition 80% AAaq (g) 360.0 (mol) 4.00 80% PEA-5 (g)140.0 (mol) 0.40 48% NaOHaq (g) 16.67 (mol) 0.20 35% SBSaq (g) 100.6(g/mol) 8.0 15% NaPSaq (g) 117.4 (g/mol) 4.0 Water (g) 0.0 Duration of(min) dropwise addition 80% AAaq 0–180 80% PEA-5 0–180 80% NaOHaq 0–18035% SBSaq 0–180 15% NaPSaq 0–210 Water 0–↑ Polymerization and (° C.) 90ageing temperature Aging time (min) 30 Degree of (%) 5.0 neutralizationafter dropwise addition After treatment 48% NaOHaq (g) 150.0 (mol) 1.80Final degree of (%) 50.0 neutralization Charged solid (%) 43.03component Polymerization SUS2.5L kettle Stirring vanes Paddle vanesFinal charge (g) 1154.71

Example 44

A polymer (44) was obtained by following the procedure of Example 31while using maleic anhydride (hereinafter referred to as “100% MA”) as athird monomer component. The prescriptions for this polymer aresummarized in Table 16 below.

The polymer (44) consequently obtained was measured for molecularweight, value S, value b, value q or value Q, Ca-binding capacity, claydispersing ability, and compatibility with a liquid detergent. Theresults are shown in Tables 18 and 20 below.

TABLE 16 Example 44 Polymer (44) Initial charge of (g) 297.0 purifiedwater Dropwise addition 80% AAaq (g) 300.0 (mol) 3.33 100% MA (g) 16.9(mol) 0.17 80% IPN-10 (g) 175.0 (mol) 0.27 48% NaOHaq (g) 30.65 (mol)0.37 35% SBSaq (g) 86.2 (g/mol) 8.0 15% NaPSaq (g) 100.6 (g/mol) 4.0Water (g) 0.0 Duration of (min) dropwise addition 80% AAaq 0–180 100% MA0–110 80% IPN-10 0–180 80% NaOHaq 0–180 35% SBSaq 0–180 15% NaPSaq 0–210Water — Polymerization and (° C.) 90 ageing temperature Aging time (min)30 Degree of (%) 10.0 neutralization after dropwise addition Aftertreatment 48% NaOHaq (g) 122.5 (mol) 1.47 Final degree of (%) 50.0neutralization Charged solid component (%) 43.03 Polymerization kettleSUS2.5L Stirring vanes Paddle vanes Final charge (g) 1128.85

Example 45

A polymer (45) was obtained by following the procedure of Example 31while using 100% methacrylic acid as a third monomer component(hereinafter referred to as “100% MAA”). The prescriptions for thepolymer are summarized in Table 17 below.

The polymer (45) consequently obtained was measured for molecularweight, value S, value b, value q or value Q, Ca-binding capacity, claydispersing ability, and compatibility with a liquid detergent. Theresults are shown in Tables 18 and 20 below.

TABLE 17 Example 45 Polymer (45) Initial charge of (g) 214.0 purifiedwater Dropwise addition  80% AAaq (g) 225.0 (mol) 2.50 100% MAA (g) 60.0(mol) 0.70  80% IPN-10 (g) 75.0 (mol) 0.11  48% NaOHaq (g) 13.32 (mol)0.16  35% SBSaq (g) 75.7 (g/mol) 8.0  15% NaPSaq (g) 88.3 (g/mol) 4.0Water (g) 0.0 Duration of (min) dropwise addition  80% AAaq 0–180 100%MAA 0–180  80% IPN-10 0–180  80% NaOHaq 0–180  35% SBSaq 0–180  15%NaPSaq 0–210 Water — Polymerization and (° C.) 90 ageing temperatureAging time (min) 30 Degree of (%) 5.0 neutralization after dropwiseaddition After treatment 48% NaOHaq (g) 120.0 (mol) 1.44 Final degree of(%) 50.0 neutralization Charged solid component (%) 43.03 Polymerizationkettle SUS2.5L Stirring vanes Paddle vanes Final charge (g) 871.33

Comparative Example 5

In a separable flask having an inner volume of 1000 ml and provided witha stirrer, a condenser, a thermometer, a nitrogen inlet tube, and adropping funnel, 200 g of an aqueous 63.87 mass % IPN-10 solution wasplaced and, with the interior of the flask displaced with nitrogen, theaqueous solution was heated as stirred to 65° C. At the point that thetemperature reached a prescribed level, 1.58 g of an aqueous 30 mass %hydrogen peroxide solution was introduced all at once. Then, 32.61 g of100 mass % acrylic acid, 29.29 g of an aqueous 2.1 mass % L-ascorbicacid solution, and 17.22 g of an aqueous 3 mass % mercapto propionicacid solution were respectively added dropwise to the solution in theflask. The acrylic acid monomer and the mercapto propionic acid wereadded dropwise over a period of 60 minutes and the L-ascorbic acid wasadded dropwise over a period of 90 minutes. After completion of thedropwise addition of the aqueous L-ascorbic acid solution, the resultantreaction solution was left aging at the same temperature for 120 minutesto complete the polymerization and obtain a comparative polymer (5).

The comparative polymer (5) was measured for molecular weight, value S,value b, value Q, Ca-binding capacity, clay dispersing ability, andcompatibility with a liquid detergent. The results are shown in Tables18 and 19 below.

Comparative Example 6

In a separable flask having an inner volume of 500 ml and provided witha stirrer, a condenser, a thermometer, a nitrogen inlet tube, and adropping funnel, 167.24 g of purified water was placed and, with theinterior of the flask displaced with nitrogen, the water was heated asstirred to 95° C. 28.9 g of an aqueous 3 mass % ammonium persulfatesolution, 82.67 g of an aqueous 50 mass % IPN-25 solution, and anaqueous solution resulting from mixing 8.25 g of an aqueous 80% acrylicacid solution with 48.75 g of 40% ammonium acrylate were respectivelyadded dropwise to the solution in the flask. The IPN-25 and the acrylicacid monomer were added dropwise over a period of 120 minutes and theaqueous ammonium persulfate solution was added dropwise over a period of150 minutes. After completion of the dropwise addition of the IPN-25 andthe acrylic monomer, the resultant reaction solution was left aging atthe same temperature for 30 minutes to complete the polymerization.After the polymerization, the reaction solution was made by the additionof 1.5 g of an aqueous 28% ammonia solution to form a comparativepolymer (6).

The comparative polymer (6) was measured for molecular weight, value S,value b, value Q, Ca-binding capacity, clay dispersing ability, andcompatibility with a liquid detergent. The results are shown in Tables18 and 19 below.

Comparative Example 7

In a separable flask having an inner volume of 500 ml and provided witha stirrer, a condenser, a thermometer, a nitrogen inlet tube, and adropping funnel, 174.2 g of purified water was placed and, with theinterior of the flask displaced with nitrogen, the water was heated asstirred to 100° C. At the point that the temperature reached the statedlevel, 32.5 g of an aqueous 3 mass % sodium persulfate solution, 82.67 gof an aqueous 50 mass % IPN-10 solution, and an aqueous solutionresulting frommixing 8.25 g of an aqueous 80% acrylic acid solution with56.2 g of 37% sodium acrylate were respectively added dropwise to thesolution in the flask. The IPN-10 and the acrylic acid monomer wereadded dropwise over a period of 120 minutes and the aqueous sodiumpersulfate solution was added dropwise over a period of 150 minutes.After completion of the dropwise addition of the IPN-10 and the acrylicacid monomer, the resultant reaction solution was left aging at the sametemperature for 30 minutes to complete the polymerization. After thepolymerization, the resultant reaction solution was made by the additionof 7.43 g of 48% sodium hydroxide, to yield a comparative polymer (7).

The comparative polymer (7) consequently obtained was measured formolecular weight, value S, value b, value Q, Ca-binding capacity, claydispersing ability, and compatibility with a liquid detergent. Theresults are shown in Tables 18 and 19 below.

Comparative Example 8

In a separable flask having an inner volume of 1000 ml and provided witha stirrer, a condenser, a thermometer, a nitrogen inlet tube, and adropping funnel, 312.9 g of purified water was placed and, with theinterior of the flask displaced with nitrogen, the water was heated asstirred to 100° C. At the point that the temperature reached the statedlevel, 68.9 g of an aqueous 10 mass % sodium persulfate solution, 32.5 gof an aqueous 80 mass % IPN-10 solution, and an aqueous resulting frommixing 15.6 g of an aqueous 80% acrylic acid solution with 332.1 g of37% sodium acrylate were respectively added dropwise to the solution inthe flask. The IPN-10 and the acrylic acid monomer were added dropwiseover a period of 120 minutes and the aqueous sodium persulfate was addeddropwise over a period of 150 minutes. After completion of the dropwiseaddition of the IPN-10 and the acrylic monomer, the resultant reactionsolution was left aging at the same temperature for 30 minutes tocomplete the polymerization and obtain a comparative polymer (8).

The comparative polymer (8) consequently obtained was measured formolecular weight, value S, value b, value Q, Ca-binding capacity, claydispersing ability, and compatibility with a liquid detergent. Theresults are shown in Tables 18 and 19 below.

TABLE 18 Monomers A/B/C (charge ratio, Molecular Pol- weight weight,ymer ratio) Monomer A Monomer B Monomer C Mw (31) 35/65/0 AA IPN-10 —23000 (32) 80/20/0 AA IPN-10 — 6500 (33) 72/28/0 AA IPN-10 — 8400 (34)72/28/0 AA IPN-10 — 14000 (35) 65/35/0 AA IPN-10 — 15000 (36) 50/50/0 AAIPN-10 — 15000 (37) 72/28/0 AA IPN-10 — 12000 (38) 65/35/0 AA IPN-10 —9100 (39) 90/10/0 AA IPN-10 — 5300 (40) 80/20/0 AA IPN-50 — 5800 (41)72/28/0 AA IPN-50 — 6500 (42) 90/10/0 AA IPN-50 — 7700 (43) 72/28/0 AAPEA-5 — 6500 (44) 60/35/5 AA IPN-10 MA 14000 (45) 60/20/20 AA IPN-10 MAA7600

TABLE 19 Monomers A/B/C (charge Com- ratio, Molecular parative weightMonomer weight, polymer ratio) A Monomer B Monomer C Mw (5) 25/75/0 AAIPN-10 — 92000 (6) 35/65/0 AA IPN-25 — 17000 (7) 35/65/0 AA IPN-10 —5900 (8) 80/20/0 AA IPN-10 — 6000

TABLE 20 Value b Binding Dispersing Example Polymer Value s (40%)ability ability Value q Value Q Compatibilty 31 (31) 5 1 105 0.3 —  55 ∘32 (32) 9 <1 215 0.5 0.008 — ∘ 33 (33) 8 1 205 0.5 0.004 — ∘ 34 (34) 12<1 215 0.4 0.002 — ∘ 35 (35) 13 <1 215 0.3 0.003 — ∘ 36 (36) 7 1 170 0.3— 145 ∘ 37 (37) 11 <1 225 0.4 0.003 — ∘ 38 (38) 17 <1 200 0.4 0.005 — ∘39 (39) 16 <1 220 0.4 0.010 — ∘ 40 (40) 16 1 210 0.4 0.089 — ∘ 41 (41)11 <1 200 0.4 0.078 — ∘ 42 (42) 20 <1 215 0.4 0.073 — ∘ 43 (43) 12 1 1950.3 — 190 ∘ 44 (44) 18 1 235 0.3 0.005 — ∘ 45 (45) 16 1 210 0.4 0.002 —∘ Comparative Comparative Example polymer  5  (5) 0 3 60 0.2 —  4 ∘  6 (6) 0 11 90 0.3 —  20 ∘  7  (7) 0 4 85 0.3 —  24 ∘  8  (8) 0 8 195 0.4—  15 ∘

The (meth)acrylic acid type polymer of this invention, in spite of arelatively large molecular weight as compared with the conventionalpolymer possessing an anti-gelling property, exhibits not only highchelating ability and dispersing ability but also a better anti-gellingproperty than the conventional polymer. Particularly by satisfying thequantity S representing the quantity of a sulfur element introducedspecified above and fulfilling the value R, the iron ion concentration,and the value Q representing the anti-gelling ability mentioned above,the polymer permits a marked decrease in the impurity content. Thepolymer possesses high quality and excels in stability of preservationwhich is free from such problems as degradation of performance andprecipitation of an impurity during the preservation at a lowtemperature. Thus, it can be advantageously applied to such uses as adispersant, a descaling agent, and a detergent builder. Moreover, it ishighly advantageous in terms of cost over the conventional polymer.

The method for the production of a (meth)acrylic acid type polymer ofthis invention can produce a polymer of a low molecular weightefficiently under the condition of such a high concentration as hasnever been attained heretofore. By performing the polymerization at alow temperature over a long span of time, this method is enabled torepress the emission of sulfur dioxide gas. Then, by decreasing thequantity of an initiator (preferably also by lowering the degree ofneutralization in the process of polymerization), the method allows theoccurrence of an impurity to be repressed. By this method, it is madepossible to produce a (meth)acrylic acid type polymer of a markedlyenhanced performance. The produced (meth)acrylic acid type polymerentails neither degradation of performance nor precipitation of animpurity during the preservation at a low temperature. Further, it canretain the high performance endowed during the course of productionstably and constantly without being influenced by the environment ofstorage (namely, it can manifest fully satisfactorily the inherentperformance without being degraded).

Since this method enables the initiator system to function highlysatisfactorily in the polymerization at a low temperature which isapparently regarded as deficient in productivity, it obviates thenecessity for adding an excess initiator to the reaction system ofpolymerization. It is, therefore, capable of repressing the rise of costfor the production of the polymer and exalting the efficiency ofproduction in addition to repressing the emission of sulfur dioxide gasand the precipitation of an impurity.

Further, by the method of this invention, it is made possible to obtaina (meth)acrylic acid type polymer which has the value S representing thequantity of a sulfur element introduced, the value R, the iron ionconcentration, the value Q representing the quantity of an anti-gellingability, and further the weight average molecular weight invariablyfalling in the prescribed ranges. The polymer manifests variousproperties such as dispersibility, chelating ability, and anti-gellingproperty most effectively. The polymer of this high quality can beobtained by the polymerization at a high concentration in one stepwithout entailing any addition to the quantity of an initiator. Themethod, therefore, greatly exalts the productivity as by omitting thestep of concentration and effectively represses the rise of the cost ofproduction.

The detergent of this invention contains the (meth)acrylic acid typepolymer described above. Thus, it forms a high-performance detergentbuilder which combines dispersibility, chelating ability, andanti-gelling property. It entails neither degradation of performancewith time nor precipitation of an impurity during the preservation at alow temperature and retains stably constantly the high performanceendowed during the course of production without being influenced by theenvironment of preservation. This the product of this invention cancontribute markedly to the enhancement of the quality of a detergent.

The unsaturated polyalkylene glycol type copolymer of this inventionpossesses high chelating ability and dispersibility and exhibits abetter anti-gelling property than the conventional polymer. Particularlyby satisfying the value S representing the quantity of a sulfur elementintroduced which is defined above, it is enabled to repress theoccurrence of an impurity markedly. This polymer possesses high qualityand excels in stability of preservation and avoids entailing suchproblems as degradation of performance and occurrence of an impurityduring the preservation at a low temperature. Thus, it can beadvantageously applied to such uses as a dispersant, a descaling agent,a detergent builder, and a cement additive. Moreover, it is highlyadvantageous in terms of cost as compared with the conventional polymer.

By the method for the production of an unsaturated polyalkylene glycoltype copolymer of this invention, it is made possible to produceefficiently the polymer of a low molecular weight under the condition ofsuch a high concentration as has never been attained by the conventionalmethod. Further, by performing the polymerization at a low temperaturefor a long time, it is made possible to repress the occurrence of sulfurdioxide gas. The occurrence of an impurity can also be repressed bydecreasing the quantity of an initiator (preferably also by lowering thedegree of neutralization during the process of polymerization). By thesemethod, it is made possible to produce an unsaturated polyalkyleneglycol type copolymer of markedly enhanced performance. The producedunsaturated polyalkylene glycol type copolymer entails neitherdegradation of performance nor precipitation of an impurity during thepreservation at a low temperature. It also is capable of stablyretaining constantly the high performance endowed during the course ofproduction without being influenced by the environment of preservation(namely, the inherently owned performance can be manifested fullysatisfactorily without being impaired).

Since the method of this invention enables the initiator system tofunction highly satisfactorily in the polymerization at a lowtemperature which is apparently regarded as deficient in productivity,it obviates the necessity for adding an excess initiator to the reactionsystem of polymerization. Thus, it can repress the rise of the cost ofproduction of the polymer and exalt the efficiency of production inaddition to curbing the emission of sulfur dioxide gas and theprecipitation of an impurity.

By the method of this invention, it is made possible to obtain anunsaturated polyalkylene glycol type copolymer which has the value Srepresenting the quantity of a sulfur element introduced and the weightaverage molecular weight confined within the stated ranges. The polymermanifests various properties such as dispersibility, chelating ability,and an anti-gelling property most effectively. Moreover, this method iscapable of producing the polymer of such high quality at a highconcentration in one step without entailing an increase in the quantityof an initiator. Thus, it is capable of markedly exalting productivityas by omitting a step of concentration and effectively repressing therise of the cost of production.

The detergent of this invention contains the unsaturated polyalkyleneglycol type copolymer described above. Thus, it forms a high-performancedetergent builder which combines dispersibility, chelating ability, andan anti-gelling property. It entails neither degradation of performancewith time nor precipitation of an impurity during the preservation at alow temperature and stably retains constantly the high performanceendowed during the course of production without being influenced by theenvironment of preservation. Thus, it can greatly contribute to theenhancement of the quality of a detergent.

The entire disclosure of Japanese Patent Application No. 2001-307757filed on Oct. 3, 2001 and No. 2002-180455 filed on Jun. 20, 2001including specification, claims, drawings, and summary are incorporatedherein by reference in its entirety.

1. An unsaturated polyalkylene glycol type copolymer, wherein thecopolymer is produced by copolymerizing a (meth)acrylic acid typemonomer A and an unsaturated polyalkylene glycol type monomer B, thecopolymer possesses sulfur oxygen acid at the terminal thereof, and thevalue S representing the quantity of the sulfur element introduced whichis defined by the formula, S=(quantity of S contained in thepolymer)/(total quantity of S)×100, is not less than 3; said unsaturatedpolyalkylene glycol type copolymer is a water-soluble polymer.
 2. Acopolymer according to claim 1, wherein a monoethylenically unsaturatedmonomer C capable of copolymerizing with the monomers A and B iscopolymerized.
 3. A copolymer according to claim 1, wherein the hue(value b) of an 40 mass % aqueous solution is not more than
 2. 4. Acopolymer according to claim 1, wherein the unsaturated polyalkyleneglycol type monomer B is at least one member selected from the groupconsisting of compounds formed by adding 1–300 mols of an alkylene oxidehaving 2–18 carbon atoms to 1 mol of an unsaturated alcohol.
 5. Acopolymer according to claim 4, wherein the alkylene oxide is selectedamong styrene oxide, ethylene oxide, and propylene oxide, and theunsaturated alcohol is selected from 3-methyl-3-buten-1-ol,3-methyl-2-buten-1-ol, 2-methyl-3-buten-2-ol, or an allyl alcohol.
 6. Acopolymer according to claim 5, wherein the alkylene oxide is ethyleneoxide and/or propylene oxide, and the unsaturated alcohol is3-methyl-3-buten-1-ol and/or allyl alcohol.
 7. A copolymer according toclaim 1, wherein the copolymer is produced by copolymerizing the(meth)acrylic acid type monomer A and the unsaturated polyalkyleneglycol type monomer B using as an initiator combination of one or morespecies respectively of a persulfate and a bisulfite.
 8. A copolymeraccording to claim 7, wherein the bisulfite is used in an amount in therange of 0.5–5 mass parts, based on one mass part of the persulfate. 9.A copolymer according to claim 7, wherein the persulfate is sodiumpersulfate and the bisulfite is sodium bisulfite.
 10. A copolymeraccording to claim 1, wherein the copolymer has a degree of gelation, q,of not more than 0.1 when the Ca-binding capacity is not less than 200.11. A copolymer according to claim 1, wherein the copolymer has a valueQ=(Ca-binding capacity)²/degree of gelation q/10⁵ of not less than 30when the Ca-binding capacity falls short of 200.